I got mine serviced by Mark Hama in the Atlanta, GA area (you can google him). He's a retired Yashica/Kyocera repair guy but he does a lot of different cameras, especially older ones. Mine came out great.
Beware the bottom loaders aren't created equal. My M2 is a lot easier to load than my IIIf. And I HAVE the appropriate tool too. Loading that thing requires talent and practice. I think the IIIf and the Summitar are nice choices, though the Elmar 50/3.5 is tempting because it is so iconic. Also these rangefinders may be harder to focus today than they once were because of degradation of the rangefinder over time. Not sure what that would cost to fix. On the other hand finding someone to fix your Leica III is a lead pipe cinch compared to finding someone to fix your Contax IIA or IIIA. I think Henry Scherer is about the only one that can really fix those things.
The III's (IIIc, IIIf, IIIg if your wealthy) can be rewarding cameras to use, but if you really want it for taking pictures rather than experiencing 1940s technology, go with an M2 or M3. Not as pretty, but much better to use in my opinion. And you can use LTM lenses with a screwmount to M adapter. You can get Leica ones at a cost or non Leica ones cheap. You might look cooler with the IIIf though ;-)