It totally depends on what you want, you can get a pipe that will give you nothing but topend or you can get one that will give you nothing but bottom end and anything in between. There are a lot of pipes out there and each one is a little different. I chose a Trinity Racing pipe (not a slip on I got the full exhaust), they claim a 5 horse gain and increased power across the band. I ride mostly wooded trails and I really don't need any more power, I am mostly between 2nd and 3rd gear and if I could just be in one as opposed to being in the middle it would be nice. I also agree if you have to ask what is involved in changing it then you better have someone do it. For the Trinity you have to put the pipe on, rejet it, and remove the airbox lid and screen. Not a lot of work but easier if you know what to do.
Balzak