You do not have to remove the entire ignition switch (incl. the housing) as long as you are able to turn the key!
If you take a close look at your ignition lock, you can see two little round spaces/opening between the gray part of the ignition lock itself and the black cover around it.
If you turn the key, these spaces will rotate over a similar sized "shaft". At the bottom of this "shaft" is a locking pin that needs to be depressed in order to be able to get the lock cylinder out.
This lock cylinder is the part that makes it impossible to turn the key so now and then. As long as you can turn the ignition lock, you can have someone with the proper tool (a U-pin that can be stuck in with a certain size and tapped ends) to get it out easy.
If you try to stick in an improper pin, you can damage the locking pin and you will have to face the fact to get out the steering column.
My advice is to go to a MB dealer and let them get it out; it is a peace of cake (as long as the lock can still be turned). BTW: do not lubricate the lock with anything at all; it will make the lock unusable; you will not be able to turn it anymore afterwards.
I do not know whether there is a doc. about this procedure, but you better do not try it yourself (this is about the #1 do-it-yourself-screw-up-mistake one can make).
If you go to the dealer, they should be having a temporary lock cylinder to install (we have them as well, since these locks tend to break down every 2-300.000km). The dealer is able to order a new ignition lock by chassis#; it will take a few weeks, but then you get a lock that fits the original key.
with a minor 600+k