When I had this problem with my '86, I had to remove the old material and backing and replace with new. You can get headliner material by the yard in a variety of colors from JoAnn Fabrics for about $10/yard (it's 3' wide, so one yard should do you) and a can of "Heads Up!" (kid you not...) from Pep Boys or other auto parts stores. Do NOT use the 3M fabric adhesive - it's not heat-tolerant, as I discovered the hard way. "Heads Up!" works wonders... my headliner looks absolutely brand new.
If the later C4 panels are like the earlier ones, the fabric is glued to a foam board which is either pressed or velcro'd onto the roof panel. I used a butter knife (rounded end, dull edge) to gently pry the board out of the panel; after that, it was simply a matter of pulling off the old fabric and getting rid of as much of the old foam backing as possible. Probably took me an hour and a half, including re-doing it because I used the wrong adhesive. Then you have to let it dry overnight and just press it back into place.
It's really not as hard as I made it sound... but I have friends who have tried to put back just the hanging fabric, and it doesn't look good at all.
[RICHR]
