That’s a good question. I will try to answer it as quickly as possible.
To unlearn your current way of typing, you will need to put some hours to learn how to type properly (around 20 hours before you will be able to forget your old ways of doing things).
RSI — I hadn’t RSI symptoms before I switched, so can’t comment on that. The only thing I would recommend is using regular mechanical keyboard WITHOUT wrist pad! When you are typing, your hands must be in the air, or else you can have pain in your pinky.
Keyboard — I don’t think that there is much difference what keyboard you use. I used for some time Microsoft Sculpt Ergonomic keyboard, but I didn’t liked it as much as simple mechanical keyboard.