Vincent, I think you will find that getting the F thoroughly cleaned and repaired will be the correct choice. A few years back I wanted one of the old Mamiya Press cameras and just couldn't find one that was in superb condition unless I didn't want to eat for a couple of months, and even then it wasn't a for sure thing. Instead, I purposely looked for one in as good of cosmetic condition as I could find that was essentially broken and put on a shelf.
Finally found that "perfect" body and after paying as much for a CLA (done by one of the best Mamiya Press guys around) as I did the camera, I have a camera that is as good as the day it came out of the factory and it works and operates EXACTLY like it should. When you get your F back, I think you will be very, very happy with the results and have the confidence that you have one of the best cameras around and a wonderful piece of photographic history.