It does not sound to me like you need more training in specific Christian arguments to stay sane. You have already figured things out despite being brought up in a situation that massively tilted the scales in favor of christianity. I doubt there is any chance they could now convince you if they had to fight on a level field. After all, it's not like they've been holding back their best arguments this whole time.
But you are going to be in a situation where they apply intense social pressure and reinforcement towards converting you. On top of that, I'm guessing maintaining your unbelief is very practically inconvenient right now, especially for your relationship with your dad. These conditions are hazardous to rationality, more than any argument they can give. You have to do what MixedNuts says. Just remember you will consider anything they say later, when you have room to think.
I do not think they will convert you. I doubt they will be able to brainwash you in a week when you are determined to resist. Even if they could, you managed to think your way out of christian indoctrination once already, you can do it again.
If you want to learn more about rationality specific to the question of Christianity, given that you've already read a good amount of material here about rationality in general, you might gain the most from reading atheist sites, which tend to spend a lot of effort specifically on refuting Christianity. Learn more about the Bible from skeptical sources, if you haven't before you'll be pretty amazed how much of what you've been told is blatantly false and how much about the bible you don't know (for instance, Genesis 1&2 have different creation stories that are quite contradictory, and the gospels' versions of the resurrection are impossible to reconcile. Also, the gospels of Matthew and Luke are largely copied from Mark, and the entire resurrection story is missing from the earliest versions of Mark.) I unfortunately don't know a source that gives a good introduction to bible scholarship. Maybe someone else can suggest one?
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A list of some posts that are pretty awesome
I recommend the major sequences to everybody, but I realize how daunting they look at first. So for purposes of immediate gratification, the following posts are particularly interesting/illuminating/provocative and don't require any previous reading:
More suggestions are welcome! Or just check out the top-rated posts from the history of Less Wrong. Most posts at +50 or more are well worth your time.
Welcome to Less Wrong, and we look forward to hearing from you throughout the site.
(Note from orthonormal: MBlume and other contributors wrote the original version of this welcome message, and I've stolen heavily from it.)