I placed the link to my diagnostic article in another thread. In it the fault code recovery is described for your exact car a 97 E320. The method is as follows:
"The procedures for pulling Fault Codes go like this (See Chart 3): Turn on the ignition, and set the left temperature to "HI" and the right temperature to "LO." Then, simultaneously press buttons "Rest" and "EC" for five or more seconds. All of this must be done within 20 seconds. The "Recirculate" button will flash its LED. The screen will then go blank, and the first code can be brought up by pressing the right "AUTO" button."
The rest of the article can be seen at:
http://www.babcox.com/editorial/ic/ic40142.htm
As to where to find a good rebuilt pushbutton controller, try Beckman Technologies. They are located in North Carolina. Being at home I don't have their number.