Rangefinder assembly is the most expensive and hard to repair part of M3 (and probably of any Leica or RF camera). I would not hesitate to pick a mechanically abused M3 to get one revived by any of Leica repair masters (Youxin, Sherry or DAG come to mind in US, others in Europe), but once RF is seriously flawed - that puts one out of question.
You may easily pick a good one for about 600 US$ online, make one through a good CLA (Youxin ranges from 80 to 250 US$ is a major replacement needed) and have a perfect, reliable M3 to run for another few decades...