In California, I can recommend...

Pro Camera Service in Thousand Oaks. They have (or, had?) a technician there who specialized in the old Nikon and Leica bodies. Caveat: I haven't taken anything to these guys since I left So. Cal. Many years ago.

and,

Apex Camera Repair
(925) 933-6016
1295 Boulevard Way
Walnut Creek, CA 94595

and,

Apollo Camera
(510) 891-9486
1411 Webster St
Oakland, CA 94612

This last however, I give only a guarded recommendation...I take stuff here when I need/want something done fast and it doesn't have a lot of sentimental value - or, Wally (at APEX) won't do it. They are fast, have great prices and have a few technicians that are spooky good. The only problem is that it is sometimes difficult to get the person at the counter to understand what you want done. For example, I once took a LF lens in shutter. I left both the lens cells in the shutter because, I walked in off the street on impulse and hadn't given it any thought - and didn't want to carry the cells around loose in my pack. Anyway, I wanted the shutter to be CLA'd. They instead cleaned the glass....to their credit however, they remedied the situation by doing the CLA that night at no charge and I had what I wanted. Total time: 3days.