There is no tutorial on how to bypass gameguard. I'm not even sure if anyone has done this yet. GameGuard (at least the newer 10xx revisions) is in fact a rootkit. It hooks itself to some dlls in ring0 so you might want to start reading about kernel and ring0. I've read about that in another forum. Probably not allowed to post link. The best 'solution' so far that I've heard of is get a clone of affected dlls before GG hooks onto them and then call whatever function you need from your cloned dll. This might work for script languages like AutoIT and such but won't bypass GG in general afaik. I have to admit, this is beyond my knowledge too. I can't do this (yet ;) ).
Google "gameguard 101"