Hello all. I have an opportunity to buy a 1983 300 CD. The owner says it needs a transmission and is having problems up-shifting. The previous owner installed a junkyard special 3 years ago and the car drove fine for 2. The car is clean otherwise with no rust (good for the North East) and has ~200k on the clock. I will be looking it over more closely, but what is the best approach for replacing the tranny? MB dealer my best bet? Any ballparks on cost?

Anything else I should look for when I go to look the car over? I will be brining the car to my mechanic (it still drives) but wanted to look for big issues beforehand if possible.

Thanks,
M