This thread has the wording for the "filled for life". It's in Gilly's post and it is worth a read if you want to laugh.
1999 S500 with 722.6 Automatic Transmission Filled for life?
Some other posts mentioned that the new MB fluid change advice is not in a TSB but a WIS and it may be a general on for all MB transmissions. Some one here probably knows what is means but the "S" is Service I think.
If you're only getting 15% from the dealer that did all your service that isn't much of a deal. It can't hurt to ask for more since it failed under their care.