Yep, that's why the glass is out; I put a new headliner in yesterday and the interior has been out of the car so long, I couldn't remember for sure the correct order of putting it back together. I was pretty sure it was glass first, but the body assembly manual insinuates that the dash pad goes in first. To me it seems like the lesser of two evils to put the pad and trim in than try to work the gasket in with so little space, and that seems to be the consensus.
Pads are easy. I like mark the windshield where the screw holes are, then slide the pad in, mark the pad, slide the pad out and punch 1/4" holes for the screws, and install the pad. Makes the whole installation no drama.
Oh- If you've ever tried to pull the seal rope on a glass with the pad installed, you'll know it's better to do the glass first.