I did it. It was necessary to replace the tumbler and the cover only, because I found fresh switch+lock there, thanks to PO. I took the whole assembly out but didnīt have to replace them, the time was not wasted because I know now how I can replace e.g. the switch only . Iīve never pulled the IP out before, it took two hours with all hesitating and thinking and test driving, replacing the switch or the whole assembly is definitely DIY.
All the info to do the replacement can be found in this great forum. Very rewarding experience, and now instead of two worn out keys Iīve one new MB key that fits to all locks!