AS Gilly is trying to say, it's tough for us to give a solid diagnosis from afar when it comes to something as complex as that 722.6.
However, you could talk to the shop about a potential repair as opposed to replacement. Talk to them about replacing the conductor plate and updated ETC (Electronic tranny control) unit. It is not unusual for there to be very fine material in the fluid, but chunks certainly can be bad news.
A faulty conductor plate will cause the tranny to go into limp home mode. Then it is stuck in gear.
If you need extensive repairs, you should talk to the Zone Rep about MB pitching in a few bucks. If you're not the original owner, you're probably out of luck, but you should ask anyway.
1998 C230 "Black Betty"