An M3 in good condition is a camera that has always a market for it, and the small signs you speak of make me think it could be rated as a "B" or "B-" in collectors terms.
I think (reasoning in Euro) that the BODY could easily fetch, like is, something around 6-700 Euros (basing my evaluation on prices at european shops: M3, as I said, are always on the market, in lot of conditions, variants, prices...).
The LENS is a separate item to deal: but you ought to specify which Summicron 35 is it: it can be with the "goggles" (optical attachment that enlarged the VF field, that is for 50-90-135) or not (in this case, isn't there a separate external viewfinder shoe-fitting ?).
And it can be of various version, depending on age... can be a "Wetzlar" model, a "Canada" model, a "8 element" a "6 element"... it was a famous lens which had many many variants: difficult to give an approx value without (A) Serial number (B) Detailed description and/or a pair of pictures.
As you say, a restoration can be costly, and my idea is that it doesn't worth if the goal is SELLING : difficult you can get paid for it... even if the camera "looks as new" it couldn't probably go to the TOP pricing, which is for bodies complete with original case, invoice, even the factory QC card... Roughly speaking, I'd say that a cost of, say, 3-400 Euros is difficult to be completely ADDED to the sale price you can get with "like is" selling on ebay.
Restoration is convenient if one plans to USE... M3 is a legendary and fantastic camera to use, still capable of superb shots, with a unique handling, and on which you can put a number of excellent lenses, both costly (new or used good Leica lenses), and rather cheap (some old Leica lenses, and the modern Voigtlander lenses).
Finally... you say the M3 is "around 1959" : i suppose is surely a "single stroke version" (one lever movement to advance film and cock the shutter)... can you post the serial number ?
And... welcome to this forum !! Maybe your destiny is to be a "casual member" but you really reached the right place for your questions...
