Hi Paul,
You certainly get around in your rv! Did the Ottawa MB dealer give you a breakdown of charges for the B Service which usually costs a lot more than an A anyway. The cost of doing a synthetic oil / filter change is one costly part and maybe they replace a filter or two as well. The fuel filter usually costs around 80 to 100 or so if not cleanable. Costs add up fast. They can give you a cost breakdown. I would guess their labour charges for checking hoses, brakes and the usual stuff adds a fair amount additional to material costs. I owned 2 MB cars and the B service was never less than 600$.
Regards,
Al