erm, correct me if i'm wrong....
Wouldnt it be better to buy the brakes etc if you knew they needed doing before the B Service and have them fitted? Buy original Merc parts. I have my local mechanic who will change discs and pads for £45 for me, all in.
Then just let MB do the barebone service, get ur stamp and run. If they ring you and say "sir, your brakes need changing" just laugh and tell them to go F***.
BimMerc