Looking To Rebuild

I got an 07 with about 100-150 pretty hard riding hours on it. I run Amsoil in it and change it about every four or five hours, and also clean my air filter regular. I'm looking to rebuild the motor ,mostly just to freshin it up and keep it VERY reliable. A little more power would be nice but don't wanna lose reliability. What should I make sure I replace and check over in the motor?