The lens is worth peanuts. It's not the 50/3.5 Tessar. The 50/2.8 Tessar was made as an attempt to get an extra f-stop using the same Tessar formula, but it was not a good idea. Rather getting a nice Sonnar 50/2 instead - I mean, the 50/2.8 Tessar is an average lense even when close to perfect, so using one which has haze and cleaning marks is not worth the trial.
On the camera : a dim viewfinder doesn't mean anything from the outside (grime, dust etc can make what you see pretty dark and blurred) and it's only when you remove the top cover that you'll see if this one has heavy separation of the cemented beamsplitter prism, but the rangefinder patch not overlapping with the main image probably means that the swinging plano-concave element in the rangefinder mechanism has come unglued with time : even if dirty and dim the RF patch must move and overlap with the main image when you focus the lens using the focusing wheel.
Everything can be repaired and restored on a Contax II and everything can be done through a DIY job but this is always long and sometimes difficult. If the external condition of the camera is worth it, you can think of it. But this would require a certain amount of experience at working on your own cameras, a lots a patience, some precision screwdrivers and tweezers, and the like. Don't expect to have the camera brought back to life in less than 30 or 40 hours of careful homework if you want to do something proper and durable.
From what I see on the picture the camera is in nice cosmetic condition with no dings, corrosion or mold.
