I replaced one of my center vent diaphragms last fall, and I had struggled for a while to do it through the glove box opening. I could have probably removed the bad pod, but adequately reinstalling the newly rebuilt one, and attaching the control rod would have been impossible in my opinion. I do believe there are quite a bit of things that can be done through the glove box, but I could not complete the diaphragm replacement. I decided to remove the dash. It turned out that it was much easier than I had thought, and I wouldn’t hesitate to do it again on one of my other cars.
Below are a couple of links that show the diaphragm and it’s location with the dash removed. It is an intimidating job, but one that than easily be tackled.
Good Luck!
Robert

http://home.attbi.com/~frickfamily/Dash-1.jpg

http://home.attbi.com/~frickfamily/Dash-2.jpg