>>2940581KEH is the best online camera retailer, no questions. I've bought at least a dozen cameras and lenses from them over the years and have always been satisfied. The two times there were issues (got wrong item), they handled the returns quickly and easily.
If you're looking for a camera to use as opposed to a collector's item, get their BGN grade. They rate conservatively, and there's no point spending extra for a camera in perfect cosmetic condition if you're planning to use it. Pic related, second from left is my BGN grade M3 from KEH.
Any of the 35mm lenses with goggles were designed for use with the M3. The Summicron and Summaron come to mind, but there may be others. But if 35mm is your preferred focal length, get an M4. The M3 by far the best of any Leica finder, but it's optimized for 50mm lenses and doesn't have 35mm framelines.
