It looks like the dealers vary somewhat as to their approach to this. One of the dealers I asked last week said the same 100,000 mile thingie. Others have written on here that their dealers have differing opinions.
As to the service "A", I'd say go ahead with that. The majority of the cost is the oil change, and it sounds like you are not due for another one of those yet.
The consensus of opinion on this thread is: If you have a car made between 1998 and 2005 that MB says does not need a tranny service, that is baloney, and you should have had one done at about 50,000 miles. No offense intended here, you are in the same "sinking boat" as the rest of us
MB is now singing a different tune.
I don't know where MarcusF lives, but he is somewhere in CA. He paid $338 for what sounds like the proper job on his CLK430 (same transmission as ours I do believe). BTW, Marcus is what some of us would call a "motor head" - he knows his stuff, and I think you can take his advice to the bank.
Good luck Debbi,