[Richard Curtis]

If you go with the glue route -- which I would not recommend -- know that 3M makes several different versions of their spray contact adhesive, so get the strongest available ... the last cans I bought were 3M General Trim Adhesive 08088; also have used Wurth Hi-Temp Spray Adhesive with excellent results. I doubt your suggested temp fix will work because in my experience (I've replaced five or six headliners in Merkurs), the fabric is bonded to a thin sheet of foam, which is then glued to the cardboard-type headliner. The foam has disintegrated. if you just spray glue in there, you're likely to soak through the fabric.

What's needed is to remove the headliner (easy to do, just tedious), remove all the old headliner fabric, remove as much of the gunk that's left (foam, glue, etc.) and then buy enough headliner fabric (available at upholstery shops by the yard) to do the job. Buy at least two cans of the glue (~$20/each). Spray one coat of the glue on the headliner fabric's backside, one coat on the headliner cardboard-y thing, give the glue a few minutes to dry. Then very carefully reattach the fabric and trim to fit.

A sunroof makes this just a little bit more difficult but not impossible.

There used to be an excellent upholstery shop in Newington's industrial park, where I bought fabric and glue, but they're since gone out of business.