how do i set the dashboard so that it displays the temperature?

This is a question for your local Mercedes dealer. I'd imagine there's a button on the dash -- in some cases the trip odometer button, for example, can serve multiple display functions, but without being too familiar with the Mercedes platform, I can't say for sure. A salesman at the dealership should be able to tell you over the phone.

take to dealer and let them set or read up on it in owners manual it will tell you how.