One thing in mind if you decide to glue on new headliner material to the foam backing......do not use 3m No. 77. It'll melt right through the foam like the scene in "Alien" when they cut the crab thingy's legs and the blood melted almost all the way through the hull of the ship....No. 77 did the same thing to my foam board. Read on the spray on can the cautions on using on certain materials.....removing the headliner is not too hard at all, just remover all the trim around it, plus be extra careful of the special clips on the upper rear trim at the rear window...they break easily.........you can get matching headliner material with foam backing at Joann's Fabrics, the color is almost dead on to the original......no on can tell I used it, came out real well.......but most important is the caution of finding spray on glue that does not ruin the foam board.
You can repair any indentations /holes on the foam board by gluing over them with small pieces of cardboard...in my case I used the ones from a book of matches....can't even see where I repaired the area after gluing on the material.
Bruce '87 Grand National