I spoke to a GM gunsmith (IIRC, his name was Jim Tertin) some years ago at an SCI convention, and looked over some rifles he'd done. They seemed quite nice. I don't know if he still works for GM.
Problem is, when you go to a big shop, generally speaking, you've NO idea of WHO is going to work on YOUR firearm. It might be the master gunsmith, it might be an apprentice who's just learning his trade. It's like rolling dice.
See if you can talk to one of the gunsmiths - preferably, the one who will do the actual work on your rifle - and ask him what a trigger job includes. If all he does is put in new springs, well, you can probably do that yourself.