Unfortunately, the only contract I had was a verbal one.
I guess I left out that $1050 was just my half of the deal. The used car dealer where I bought the car paid another $1050 as part of a 50% warranty that the car was under. It's good to know that I paid less than it would normally cost
(assuming he actually rebuilt it).
I'm planning on taking the car to an independent MB mechanic in Santa Rosa who has always done good work on the 280C for an honest price. (One time, he diagnosed on the phone that the points needed cleaning. After he cleaned them and adjusted the timing, it ran better than ever before or ever since. Unfortunately it had a smog check a few days later.) I'll ask him if he can verify that the tranny has indeed been rebuilt. I'm heading north too soon for the tranny to be broken in in time to take it somewhere in Santa Barbara for a service. (But I will keep Gary Semeridjian in mind, surfnvet.)
Thanks for your help, everybody! I will post it here when I find out exactly what has been going on with my car.
Santa Barbara, CA