I have a 2004 E320 4Matic wagon. I just eliminated annoying service message that kept popping up everytime I started car - I'm a doit myselfer.
Here's how I did it:
* Turn key on to Acc position (not Run position)
* Arrow (on steering wheel) up until message appears
* Push and hold reset button on dash (left of speedomoter)
* Hold for about 10 seconds until menu appears
* Use - (negative) button on right side of steering wheel to scroll down to Confirmation
* Push bottom menu button (left side of steering wheel) to see options available
* Use - (negative) button on R side of steering to scroll down to Cancel
* Push bottom menu button on left side of steering wheel
* You should get message "Service Cancelled"
You're done!