Sorry, yes, check level in P. You are correct!

I'm still worried by the amount of fluid you needed to correct the Indy's obvious "sloppy work". Is it possible that he "forgot" to change the fluid in the first place?

All I can suggest is another fluid change with a good quality synthetic fluid. If you are confident that has already occurred, take it to the real MB Dealer for a problem analysis and quote for "repairs".