I have done quite a few of those headliner jobs and the fabric is always too thick for the sunroof part. However, if you will just bend down the sunroof housing pan just in front of the interior light where the bead holds the main headliner to the top, you can add enough room for the thicker liner to slide back and forth. If you really want to remove the headliner from the sunroof here's how to do it. 1. Take loose and drop the entire main headliner assembly. 2. Open the roof to vent position and unhook the two wire-like clips by pushing them to the front of the car. 3. Reclose the sunroof and push the headliner toward the rear of the car. 4. Take the rear of the pan down by removing four of the bolts that hold it in place and lossing the other ones at the front. Turn the headliner a little sideways to get it out of the drawer it slides in and pull it out to the rear of the car. Assembly is the reverse, but make sure you have the sunroof headliner in place properly before putting the pan back up. Good luck.
Jon