Any recommendations on a reputable watch shop in Southern California for sales and/or service of vintage watches?
Jeff Stein, vintage Heuer guru but not exclusively Heuer, has posted in OntheDash that he has bought watches from them. I call that a recommendation.
You have to be really careful with them, they have had more than a few watches appear in the OF hall of shame. Many of their watches are dubiously "restored" and outright misrepresented in their online listings. Certainly not saying its all bad, just do your homework.
For sales it largely depends on what you are looking for. For good service at fair prices try Second Time Around Watch on S. Beverly in BH.