If you can spare the money and if the Leica M3 and lens are in good order, go for it!
It will be fun to shoot with this camera. The Leica M3 is one of the best M-models according to meany people. I use a M4-2 and M7.
And if you decide the Leica isn't it for you in a year or two, you'll be able to sell the M3 as easy/easier than the stuff you traded it for.
And if you decide the M3 is the camera for you, you can always get some Voightlander lenses for it if original Leica lenses are too expensive.