I always went to Val Surf in the Valley Village.... may seem like a surf shop... but the guys that run the repair shop are pretty much the raddest 50 year old former ski bums ever. They gave me one of the best race tunes I've ever had and did it free cause they were so excited that I even asked for a race tune... on a pair of demos that they also let me take out for free.
Anyway, they are rad. They know their shit. They aren't as expensive as some of the other legit shops around but after visiting pretty much every shop in LA/Orange County many many times (used to do outside sales) they were definitely my favorite most informed repair shop.