My 2002 CLK 430 decided that the part on the top of the trunk, in the center - needed to be free. It flew off (the housing) - leaving the electrical components underneath exposed. Any idea what it is and where I can purchase one?

missing cover / housing

 

That's the cover for the satellite antenna.

The part number is A129827XXXX, where the last 4 digits will be your paint color code. If the last 4 numbers are 9999, the cover will only be primed.

You'll probably need to order the cover from a dealership.

If there's a 'pick and pull' salvage yard near you, the same cover was also used on SLK and SL models as well.