Based on experience earlier this year, I would avoid Mamiya Corp. in NY and instead go to Precision Camera Works in Chicago (there are several PCW throughout the nation, which is why I mention the one in Chicago). Mamiya Corp. wanted over $800 to fix my Mamiya 7, which had a broken winder (I don't know how much the overall damage was). I turned that down and instead sent it off to PCW, which fixed my 7 for a bit less than $400, which included a rangefinder calibration and an upgrade to the 7 II finder. They also had a much faster turnaround time than Mamiya. I got my 7 back in less than two weeks, including shipping time both ways.
I talked with someone at PCW at the time and they indicated that Mamiya Corp. has shifted from repair to complete replacement of parts.