Well, since I do aircraft interiors for a living, and automotive upholstery on the side Ill post up some pictures and how to's on doing a headliner the "professional" way.
Pulled the headliner out, the only trim pieces that need to come off are the A-piller trim, and they really only need to be moved out of the way. After the sunv visors, HUD, and the 2 metal brackets in the headliner are removed the headliner will slid foward of the back to trim pieces, and you can pull it out of the either door.
Next I set everything on my table to be stripped. first removed all the trim so that the new material could be glued in place, and the trim installed back on.
The guy that tried doing this before loved duct tape and what looks to be like Seel tape. I will be removing this and gluing in and mesh if the headliner is crubled at all.
The glue I spray is Weldwood Landau top adhesive.
Cleaned off the old foam by wire brushing it off, then I glued in some material to reinforce where it was cracked. It was pretty bad in some spots.
I always glue one half at a time as you can see. Spray the glue on both sides and let it tack for 5 mintues before spreading out the material. If the glue your using is not yellow like this stuff, and you dont spray it out of a gun, then its not the right stuff!
After I had everything smoothed out I flipped it over and trimmed about 2" outside in order to fold the material over.
Then I spray glue once again on the outside of the back side of the headliner and folded the material over. Then I cut out for the brackets, HUD, and cut slits for the sun visors.
Went back in the car after that, had it back in the car within just a couple minutes since I only removed the 2 necesarry trim pieces.
Next I need to do the visors, and HUD when I get the time. Just got some material in for a set of GLHS seats so its time to start back on them.