I’ve been breaking my cameras for decades.
Here are the places with which I’ve had good luck.
Just as important as fixing the camera is that a real repairman leaves no tracks: no marks on the screw heads or anywhere to suggest that he’s been inside the camera. If you get a camera back and there are marks on it, that was a bad repair. I refer to these marks as “technician tracks.”
Before you ship anything to anyone, be sure to confirm that they really are at the address I’ve listed for them.
For current digital cameras, I always send them straight to the manufacturer’s own repair facility closest to me.
Few if any independent repair facilities are Nikon or Canon certified or trained. If they are, be sure to ask for what cameras.
For digital cameras one especially needs full access to very specialized test equipment, firmware, software and tools for in-depth service of DSLRs and point-and-shoots.
Independents can clean and do most things, but if I really break a DSLR, I send it directly to Canon or Nikon because I know they have the most complete facilities.
Canon or Nikon have referred me to local authorized independent repair shops, which also do great work. For instance, Kurt’s in San Diego has all the factory equipment for Nikon.
I’ve always had very good results with both Canon and Nikon’s repair depots. If anything wasn’t done properly the first time, a polite request got it done the second try