Does your dash have a passenger airbag or not? What colour is your interior?
I still have some dash lids lying around after I rebuild my car with an AMG interior...
I bought my new parts at the dutch MB dealer; the prices they charge are normally very fair.
The vacuum pump in the trunk of the car will stop intermittently (it has a feature to prevent from overheating).
If you can give me some more info (if possible with some digital pictures), I might be able to lead you through a DIY procedure for your vacuum problem...I might even consider to get me a return ticket and do the repair for you (1500 US$ will definitely verify the costs involved...way too expensive!)
If you don't have the passenger airbag, you have a lot of space to get to the vacuum system near the recirculation valve.