I'm not sure what you have now but I imagine that you had a tumbler problem to begin with. If you can get the key to turn the door handle can be removed without taking the door panel off. When the tumbler won't go one must get the 90deg rotation of the latch by a combination of turning the whole handle and the turning thelatch once loosened.
The tumblers come apart very simply once the handle is off and the tumbler pack can be mmoved from handle to handle. Once you are that far though it becomes plain why the tumbler quit and its easily repaired without any other parts. The tumblers wind up not being moved far enough due to wear. Just throw out the offending tumblers or file them down till they fit.
Bosch Master, ASE Master, L1
33 years MB technician