http://www.justanswer.com/mercedes/4s5sm-mercedes-benz-e350-4matic-reset-service-indicator.html
This page should help. I do know that you can't be too slow in doing each step. You have to practice over and over until you can do it with no pauses.
Make sure you do everything. For instance, you have to be in the drivers seat with all the doors closed.
Good luck.
Paul