I have a 95 c280 with the same problem. When I took mine apart the spindle wasn't detached, it was broken in half, thus the key wasn't turning anything. I don't know if you can buy a spindle so I may have to fabricate one. This could be your problem too. Its not a big deal to take it apart, just pull the door seal up and there is a hole that is in the inside of the lip from inside the door toward the locking mechanism. Just take a 4mm hex and keep turning until you can pull the lock out. The hex screw can't fall down because its sandwhiched in the door.