I have read a couple of threads on removing the dash panel vents, but have not been successful. They talked about removing the box behind the vent and then pulling some pins. In my case, the vent is loose all the way around, except for the lower right corner. I can easily move it in all directions, but can't get it off of that corner.
I tried taking the screws out of the back of the box and unhooking the vent slider, but those two things did not change anything.