I agree with FC. Probably Nikon first and for a second, uh, hard. Actually there's quite a few good guy's around servicing particular brands with alot of experience and alot of parts. I will say that of the type of repairs I've needed that were left undone for one reason or another, it was lens work being usually oil on blades, lens seals or dust, broken lens parts or meters especially in K1000's and Spotmatic's. Now if you want to collimate lenses you could possibly have a good business or you could set up a optical bench and test lenses.
Originally Posted by Trask