I own a 1994 E420 at 125000. The wiring harness has been changed about 10000 miles ago. The car started to idle really rough and stall then it just wont start without the gas pedal. When it does start it wont stay idling and will stall if you let off the gas pedal. I took it to John Holtz Mercedes of Rochester, NY and they claimed that there were numerous codes from different modules but one for throttle valve actuator as well. How much does this cost for my car?
What is the part number?
What does it look like?
Lastly how easy is it to replace?

I plan to do it myself if I can. The dealer wants $2400 for it.

Thank you in advance for all your help. I did search the forum but did not find the picture and how to remove info for my car.