Wow...I like that you've actually done it.
If you plan on redoing the install at some later point, I would suggest teh following:
1) Replace the in-dash xenarc with a quality aftermarket radio. Mount the aftermarket deck where you placed the in-dash xenarc. Since the xenarc sticks out quite a bit, the aftermarket radio would probably result in a more flush look. You could even fabricate a bezel to cover up some of the holes and redirect the air-flow;
2) Remove the COMAND unit - it's worthless;
3) Custom-mount a 7"/8" touchscreen where your COMAND unit was installed.
I hate the mercedes navigation systems. You may as well purchase a Thomas Guide and get more use out of it. Good luck.