Help! ML dashboard center A/C outlet
 

In my '99 ML320, I have partially pulled out the center-dash A/C ducts (three-in-one unit) to try to clean out the disintegrating foam inside that blows into the cabin like a greasy soot. The unit is out about a 1/2 inch on one side, but I'm afraid to just grip it 'n rip it, and I can't push it back in - it is hitting on some obstruction. How do I get this unit all the way out to clean it, and how do I put it back? Is it possilbe, or have I started something the dealer will have to finish at some very expensive hourly charges?

My wife is furious with me!!!