welcome to the forums, wow that's alot of questions!!! lol, ok as far as power mods u can do an exhaust, air filter, gear reduction if you have bigger tires (29 and up)... there's alot of good lifts, but the two that come highly recommeded are highlifter and ssatv lifts,but there are quite a few out there. The foreman can turn 28's no problem without any modifications!!!! you can put any tire on your stock wheels as long as the last number is a 12 on the tires your looking at, for example you have 25 8 12 on the front now so you can put 28 10 12 on your fronts if you want. hope that makes sense to you. as far as your warranty is concerned check with your dealer, there all different. just google all that other stuff and there's also a serch bar here and you can look at old posts that will answer most all your questions