You have a good case but I think it's with the selling dealer. It's wishful thinking but see if they'll compensate your local dealer for the work. If not, bring it up with the regional MB rep. Ideally they'll perform the deferred maintenance. You shouldn't have to settle for a letter from MB stating that lack of documentation will not affect your warranty.

How can the transmission need a fluid change at 39K miles? That's a heck of a 180 from lifetime fill.

Sixto
87 300D