If your going to pay high prices then I would buy from a Leica appointed dealer, which is what I did for my own Leica M equipment. When I accidentally damaged the viewfinder glass Leica UK included a service in the repair cost, but then indicated the camera had actually been serviced a year or two before and was in excellent mechanical condition so reduced the costs. That's an honest company for you.

In posts here on APUG David Bebbington has discussed buying screw thread Leica's and even allowing for the cost of a full service saving very significant amounts compared to many dealers shelf prices.