There are some guys on here with the procomp lift, and most of them will probably tell you it's great. But what I can guarantee you is, the majority of people on here with a lift are doing so with an Old Man Emu kit. No it isn't the best, but it is the cheapest of the "worth while lifts," if you will.
The tire will be fine. By that I mean, it will fit under there. With a 3" lift you can squeeze a 35" tire under there. The thing you need to decide is what type of tire you want to get, then figure out what size will work best for you. There are literally thousands of threads on this topic. Good luck.