I am new, so Hi everybody.

Background. I bought my daughter a 96 C220. I really like this car, (I like most mercedes) and she eventually came to understand what a great car it was. And by was I mean that she had a wreck. The front end was damaged, air bags deployed, windshield cracked by the passenger airbag, and luckily she was unhurt, as was the other driver. I'm glad I bought her a safe heavy car.
So I bought a 95 C280 to use for parts to repair her car. However, when I got the car home, it cranked and engine ran well, but transmission was shot. Loud noise at idle, stops when you have foot on brake and put it in drive. A transmission man tells me it is the planetary?

Anyway, if I wanted to replace the transmission in the C280, what models could I look for that have the same transmission?
And, are the transmissions in the C220 and the C280 not the same, and why not?