That's a shame. I had my C220 for several years and only had to do typical maintenance to it until i totaled it. I had it rebuilt but then the airbag light was on (which was not on until the MB dealer took the bumper covers off to repair them) so I got fed up with the dealer and bought an ML (big mistake). I sold it to a friend that was well aware of the rebuild and he has had no problems since.
Do a search with "tranny piston failure" and you will find several threads with info for you.