My first real camera (other than 110 instamatics) was a Leica IIIc with 50mm Summitar. There's something about the un-ergonomic shape, the heft for it's size (or lack thereof), and the sound of it's shutter that I've yet to find with any other camera. And, no matter how much it looks like a Leica, my Zorki doesn't come close to capturing that feel.
Adorama often has M series bodies listed on ebay - M3s seem to run somewhere around $500 (I haven't paid that close attention). I've never had a problem with anything I've bought from them (I've bought a fair bit of used and refurbished from them on-line and by phone) so I have no reason to believe there'd be a problem with their ebay stuff. In fact, I think they list something like a 100 day warranty.