As the titles states, I am wondering how much for this fix for the part itself and how much would you expect to pay at a shop for install? It is a car I am considering purchasing, the car is a '98 formula. private seller, says it might need a 3rd gear transmission syncro, 6 speed manual.
I think the OP is considering buying a car, not just the T56. I would say the parts would be roughly $50, and the labor between $150-$250 depending on shop rates. As mentioned, if you have to pay the shop to R&R the trans from the car, the labor rates can be 2x-3x the trans repair.
Any additional parts found bad during the repair would be in addition.