Does the key still turn the ignition and steering lock? If it does the tumbler can be fairly easily removed with a couple special tools. If the thing no longer moves it is a big problem.
With the key turned to the proper position a pin can be inserted that releases the collar which then can be unscrewed to release the tumbler. The tumbler can be ordered to match the original locks or can be changed to a workshop version for emergencies.
Bosch Master, ASE Master, L1
33 years MB technician