I replaced mine a couple of years ago. I do remember having to buy the part at the MB dealership parts department. I had to remove the center wood surrounding the shifter assembly and pry open the gear selector part and remove the shift knob to install the new part. I'm not for sure, but I think the gear selector cover comes as a sub part for the selector assembly. I can not remember the price, but I think it was around $50.
Follow the link below for information on how to remove the center wood. I posted the removal instructions a couple of days ago for another owner of an S-Class. There might be someone here that has removed the shifter assembly without removing the center wood, but in my case, I had to remove the surrounding wood.
I have the same problem, but have not found a solution yet.
I guess we will have to remove the whole shifter assembly
from the car and deassemble it. (you have a 722.6, which
is same as mine, and more difficult than the 722.3/4/5)
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