Don't pay someone $60 to do it, its best you learn to do it and save yourself that money, because it needs to be checked every few months anyway. Go the the guide Raptor450 linked, and check about the YFM350 Central forum, I think they have a picture by picture guide on it.

 

I had the 350 Big Bear (same Motor 348cc) and it always had a knocking sound while idling, but it disappeared once you reved it up abit. I just gave up trying to quess what it was.