MBenz once built his radar detector into his dashboard, with the display where the row of switches (eg hazards, head rests &c) is. He has since moved it. You may wish to check out his site, I think his address is http://www.mbenz.nl
but I'm not sure.
Also, you may wish to seek his advice before doing any further work. I reckon Mbenz has forgotten more about the C-Class than any of the rest of us have ever known.