I'm not entirely sure if it's alright to alter someone's mind to update in light of new evidence if they didn't want to update. The same goes for the 1 and 3.
But let's assume, for the sake of argument, that we accept your categorization. Or let's at least assume that the person in question doesn't mind the updating. It seems to me that there are two possible kinds of knowledge about what wireheading feels like, and we must distinguish between which one we mean.
The first kind is abstract, declarative knowledge. This may affect our (instrumental?) preferences, depending on our existing preferences. For instance, I know that people choosing where to live underestimate the effect travel times have on their happiness and overestimate the effect that the amount of space has on their happiness. Knowing this, and preferring to be happy, I might choose a different home than I otherwise would have. I presume you don't mean this kind of knowledge, as we already know in the abstract that wireheading would be the best feeling we could ever possibly experience.
The second kind is a more visceral, experienced kind of knowledge, the knowledge of what it really feels like. Knowing what it feels like to be a bat, to use Nagel's classic example. Here it becomes tricky. It's an open question to what degree you can really add this kind of a knowledge to someone's mind, as the recollection of the experience is necessarily incomplete. We might remember being happy or wireheaded, but just the act of recalling it doesn't return us to a state of mind where we are just as happy as we were back then. Instead we have an abstract memory of having been happy, which possibly activates other emotions on our mind, depending on what sorts of associations have built up around the memory. We might feel an uplifting echo of that happiness, a longing to experience it again, bitterness or sorrow about being unable to relive it, or just a blank indifference.
If an FAI simply simulates a state of mind where knowledge of the experience of wireheadedness has been added, I don't think that will change the person's preferences at all. The recollection of the wirehead state has just became an abstractly recalled piece of knowledge, without any emotional or motivational triggers that would affect one's preferences in any way.
Let me try a different tack here. Suppose you have in front of you two flavors of ice cream. You don't know what they taste like, but you prefer the red one because you like red and that's the only thing you have to go on. Now an FAI comes along and tells you that it predicts if you knew what the flavors taste like, you'd choose the blue one instead. Do you not switch to the blue one?
I presume you don't mean this kind of knowledge, as we already know in the abstract that wireheading would be the best feeling we could ever possibly experience.
Know that ...
In the comments of Welcome to Heaven, Wei Dai brings up the argument that even though we may not want to be wireheaded now, our wireheaded selves would probably prefer to be wireheaded. Therefore we might be mistaken about what we really want. (Correction: what Wei actually said was that an FAI might tell us that we would prefer to be wireheaded if we knew what it felt like, not that our wireheaded selves would prefer to be wireheaded.)
This is an argument I've heard frequently, one which I've even used myself. But I don't think it holds up. More generally, I don't think any argument that says one is wrong about what they want holds up.
To take the example of wireheading. It is not an inherent property of minds that they'll become desperately addicted to anything that feels sufficiently good. Even from our own experience, we know that there are plenty of things that feel really good, but we don't immediately crave for more afterwards. Sex might be great, but you can still afterwards get fatigued enough that you want to rest; eating good food might be enjoyable, but at some point you get full. The classic counter-example is that of the rats who could pull a lever stimulating a part of their brain, and ended up compulsively pulling it, to the exclusion of all else. People thought this to mean they were caught in a loop of stimulating their "pleasure center", but it later turned out that wasn't the case. Instead, the rats were stimulating their "wants to seek out things -center".
The systems for experiencing pleasure and for wanting to seek out pleasure are separate ones. One can find something pleasurable, but still not develop a desire to seek it out. I'm sure all of you have had times when you haven't felt the urge to participate in a particular activity, even though you knew you'd enjoy the activity in question if you just got around doing it. Conversly, one can also have a desire to seek out something, but still not find it pleasurable when it's achieved.
Therefore, it is not an inherent property of wireheading that we'd automatically end up wanting it. Sure, you could wirehead someone in such a way that the person stopped wanting anything else, but you could also wirehead them in such a way that they were indifferent to whether or not it continued. You could even wirehead them in such a way that they enjoyed every minute of it, but at the same time wanted it to stop.
"Am I mistaken about wanting to be wireheaded?" is a wrong question. You might afterwards think you actually prefer to be wireheaded, or think you prefer not to be wireheaded, but that is purely a question of how you define the term "wireheading". Is it a procedure that makes you want it, or is it not? Furthermore, even if we define wireheading so that you'd prefer it afterwards, that says nothing about the moral worth of wireheading somebody.
If you're not convinced about that last bit, consider the case of "anti-wireheading": we rewire somebody so that they experience terrible, horrible, excruciating pain. We also rewire them so that regardless, they seek to maintain their current state. In fact, if they somehow stop feeling pain, they'll compulsively seek a return to their previous hellish state. Would you say it was okay to anti-wirehead them, since an anti-wirehead will realize they were mistaken about not wanting to be an anti-wirehead? Probably not.
In fact, "I thought I wouldn't want to do/experience X, but upon trying it out I realized I was wrong" doesn't make sense. Previously the person didn't want X, but after trying it out they did want X. X has caused a change in their preferences by altering their brain. This doesn't mean that the pre-X person was wrong, it just means the post-X person has been changed. With the correct technology, anyone can be changed to prefer anything.
You can still be mistaken about whether or not you'll like something, of course. But that's distinct from whether or not you want it.
Note that this makes any thoughts along the lines of "an FAI might extrapolate the desires you had if you were more intelligent" tricky. It could just as well extrapolate the desires we had if we'd had our brains altered in some other way. What makes one method of mind alteration more acceptable than another? "Whether we'd consent to it now" is one obvious-seeming answer, but that too is filled with pitfalls. (For instance, what about our anti-wirehead?)