Spoke with the regional representative from MB yesterday about the problems mentioned and will be meeting with him shortly. He claims that regarding the squeak in the steering wheel there is a copper and carbon connector set that's used to make a contact between the horn & airbag and their electrical down stream components. He thinks this is what's making the noise, and says that, if so, it may not be solvable.
Regarding the thunk, he says that that's the 4-matic engaging, and is almost definitely not solvable, as it's working the way it's supposed to. This is about what was said here.
Not real encouraging. Anyway I'm going to meet him and go over a number of issues, on the 7th at the Seattle MB dealer's offices.
Let me know if anyone wants to hear the follow-up to this and I'll post at that time….
Many thanks for your feedback!