Just replaced the headliner in my 2014 981 Cayman, and thought I'd share the experience.
Fabric detached from the head liner panel and started sagging. Did some research and learned there's really no way to just reattach the fabric. The fabric is manufactured with a foam backing, then glued to the headliner panel. It's not possible to reglue the fabric to the foam. The glue will bleed through and look terrible.
Priced a replacement headliner panel and it was about $1,200. Took it to an auto upholstery shop and they quoted me $100 to recover the panel itself, but didn't want any part of taking the panel out of the car, as the passenger rear window needs to be removed to get the panel out of the car without bending (creasing) it. They said most people take their car to the dealer to have the panel removed, he recovers it, then the dealer reinstalls.
I decided to remove the panel myself and it really wasn't that bad. Basic process was this:
Fully recline and position the passenger seat as low as possible
Remove the center overhead light, it just pries out, disconnect the wiring connector
Remove both sun visors, no real trick to them
On the frame of the car, pull the upper half of the door rubber gasket out of its track along the roofline and from in front of the rear window
Remove the metal rain rail roof trim - there are small white plastic torx screws holding this into the frame of the car. Turn them 1/4 turn counterclockwise to disengage them, they stay clipped into the trim piece when it's removed
There are two nuts which hold the B pillar to the frame of the car. The pillar is actually the forward edge of the rear window's metal frame. To access these bolts, you will need to remove the metal "cross bar" that runs across the interior behind the seats, then remove the trim which covers the seat belt shoulder attachment point.
Once the B pillar bolts are removed, you can slide the rear window toward the front of the car to remove it. There is some black RTV sealant in the tracks which will give a little resistance, but isn't too tough. (I replaced the RTV with sealant when I reinstalled the window)
The headliner panel itself is pretty easy to remove, there are just basic clips holding it up. Careful not to lose any.
Once the headliner panel is loose, it's pretty easy to slide out of the car. I recommend covering the dash with a towel to avoid scratches.
Installation is the reverse of removal. Again, be sure to seal the rear window. The most difficult step for me was getting the rubber door gasket back into position just right. Use the driver's side as a reference.
So I replaced the headliner myself for $100. The fabric is a very close match to factory, and I'm happy with the results.
I have a question for you; how did you re-attach the rear headliner just above the rear window? There seems to be a rail with grooves in it and a ridge on the actual fabric. Any recommendations on how to do it? Great article!