I got to agree with mike and iluvmils, get the shop to fix thier mistake, then do the B2 when you get the chance. I have found most benz transmissions might have a drop here and there but the best way to determine if you have a problem is to keep a track of your fluid, you don't have to worry if it can go 30000 miles with no top up (1 pint or less).
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)