Ad two: I have no particular expertise in this area, so all I can offer is a few remarks based on what I myself do when I want to change something about my speech (e.g. my accent, but also vocabulary). Basically, it's one of those things where what you need to do is train yourself to pay attention. In order to do this, it's important not to be afraid to speak slowly. There might be an unconscious inhibition to speaking slowly for fear of appearing dumb. If you overcome that, you have time to consciously double-check what you're saying, and to consciously intervene by actively thinking about what you're going to say, and then saying it, or by stopping yourself when you feel that you're about to say something undesirable (like "like").

Also, you couldn't be old-fashioned by wearing a fedora, if I'm correct in deducing from you username that you're a girl. ;-)