If they didn't advertise the shutter problems and you decide to keep it anyway, I would ask about a partial refund.
I believe Cameraquest will service Contax IIa/IIIa bodies and their info is at http://www.cameraquest.com/repairs.htm . $195 for a CLA isn't bad and if there is no other damage or parts needed, you'll end up with a perfectly functioning camera. Stephen also has a good article on these cameras and lenses at http://www.cameraquest.com/conrf.htm . He states That the slow speeds are the first thing to go when the shutter needs servicing.
The going prices for the Zeiss lenses seem much more reasonable than comparable Leica lenses these days, plus you can also use any Nikkor RF lens 35mm or wider on a Contax body. Nikon also made longer lenses for Contax, indicated by a "C" on the underside of the barrel. Voigtlander also made lenses in the Nikon RF mount, so you could also use the 35 and wider lenses, which should be great performing lenses.