Are your black dots and scuff on the viewing/focusing screen?
This also could be a solution for you: "If neither works, there is a problem that needs to be solved. Ask KEH about footing the bill, or return the camera for a better one."
I'll second David Odess. I just got my 500 c/m back from him after a CLA. Aside from the general CLA he also fixed a rather unusual problem with the film back. Just be advised that the cost of a thorough CLA may be half or more of what you paid for your kit!
The silver lining is that his work is 1st rate and I expect the camera to operate well for years to come (I hope).