Urgent!!!!

No need to remove either window to install headliner. I can see how it would be easier to do with the window/gasket out of the way but certainly not necessary.

There is a tool that you can get from Eastwoods that is just for tucking the headliner under the window gasket. It's thin and rounded so as not to catch and tear the headliner. Apply some 3M contact adhesive to the liner and use th tool to work it under the gasket. I used a razor blade to trim the excess after the adhesive dried.