Neither is worth repairing, and you can replace the Ricoh for what it would cost to have a shop do anything to it. You may be able to use the Ricoh lens on the MZ-50, but the fine details of later K-mount variations are best left to someone other than me. If you can't use the lens, it would be worth buying a plain K-mount body for older manual focus lenses.
And, no, the camera does not matter for the darkroom, as evident from the use of such things as pinhole cameras (see Marcy Merrill's Pintoids Dead Link Removed for example). Results vary, of course, depending on the presence (and quality) of the lens.