dtwbcs,
I just complete the same project. I should have taken some photos but I didn't.

Disconnect the vent cable and remove vent cover and then the vent door. I then pulled the old foam out of the vent door. The vent door is 2 pieces of sheetmetal sandwiched together. I took a screwdriver and open up the channel that the foam goes back into. Squirt it with a little glass cleaner to make it slick and push it into the channel. Be careful because the new foam is fairly delicate. When you get it all in, lay on the floor and tap lightly around the edges with a hammer to tighten up the metal around the foam. My cable was so rusted I could not get it to open and close smoothly. I bought new replacement cables from Classic Parts. They work silky smooth. Everything works like new now.

Good luck,
Hugh
55 2nd