bad shift fork and pinion gears???

[Boostn]

Hey guys,

I have a 2002 YZ426F and I haven't taken it apart yet since new. Athough I didn't ride it for a whole year till couple months ago. Anyways, I really am getting back into riding it again. Just found out that the 5th gear would slip in and out under load. It really sucks. I did some research and I am not sure. It sounds like I might have to split the case where the shift forks and gears are

I wonder if someone could show me where can I get more info about this repair since I would like to learn to do it myself. I have some mechanic skills that I have learned myself from working on cars, but never that much on the bikes.

Oh yeah, I would have to do a through tune up and maintence on it including valve job, but hell, I missed out the 450F cam swap! I am gonna do that too! Man, can't wait to have the auto decompression again

Thanks guys