Mercedes E 320 Service questions

I took my E320 in for a Service D.  I know it entails a long inspection, but I
thought it included certain things, like an oil change, brake fluid flush and
refill and possibly other things as well.  I thought Service C was to include
replacing cabin air filters, spark plugs and wipers.  
When I went to pick up my car from Service D, they had a list of things I
"should" have done, including: replace wipers (I think they are still very
good and have no problem), change cabin air filter, change spark plugs,
have the brakes flushed, etc...
I was shocked!  This was from the dealership.  So, I'm wondering why my
Service D was $600 without anything like the brake fluid flush.

Also, I understand that Mercedes Benz no longer goes by the Service
letters (A, B, C, D and so on), but what do the Services correspond with
now (like numbers or something???  How do I know when I should have
certain things changed/replaced?  Also, why are the services so high if all
they do is look at the car?  Why weren't the spark plugs and fliters changed
the last Service?  I'm totally confused now...