Trials has completely separated itself from mountain biking and while many trials riders enjoy other types of cycling, not much trials info makes it the mainstream. Trails bikes generally have very long top tubes, short chainstays and high bottom brackets. To modify a MTB for trials, lock out the fork. eliminate all but the granny ring in the front and use a cheapo road cassette and derailleur with a very short chain. It really doesn't matter what bike you use, it will soon be destroyed. You can buy special brake pads just for trials from these guys. http://www.trialspads.com/shop/. There is usually one decent trials forum but it's a bit rough. Look around a bit and you will find it. My trials bike is a specialty machine with very wide rims, small gears and amazing brakes. It takes a while to learn the moves but really is worth it for fitness and skill building. Youtube has tons of stuff.