A local camera technician overhauled my M4-2 viewfinder and my Leicaflex SL shutter within the past decade. DAG did CLAs on three 1960-1970 R lenses (as well as a couple of older M lenses too).
In general, EVERY mechanical camera I've purchased in the past 15 years, with one exception—the Leica R6.2, has required at least a shutter CLA. I've always managed to find someone to do the work and had it done well, to my satisfaction. Was it worth it? Likely not, but economy was never the reason why I chose a particular camera, and certainly not any Leica.
If that's why you're buying an old Leica, I suggest that you should perhaps think a little differently about that proposition.
G