This is not a simple operation. There are instructions in a locksmith manual for drilling the tumbler through the key slot. I have never been able to do it. There is virtually no way to explain what to do without having the new parts in your hand.
The system is designed to be pulled apart with the key in one of the unlock positions (I haven't done one in years). A latch must be released with a special wire loop in that position. Without being able to turn the key the drilling method is designed to gut the tumbler till the latches fall in.
The way we usually do it is to drill the release pin of the steering lock. Again the way to do this is to have the new parts in hand and see where the releases are and how they come apart.
Bosch Master, ASE Master, L1
33 years MB technician