Nick,
You've seen my headliner, right? I recovered that, big PITA but worth it since it turned out the way I wanted and I'm probably the only MK2 owner with a black headliner. The headliner is molded cardboard with foam backed vinyl glued to it. You can pull the vinyl off but then the fun and frustration begins

You have to completely remove the glue and foam.
The only way I found to do this is to rub it off by hand, or I should say by finger tip. Once you get a little ball going it kinda sticks to itself... but not for long :x Just keep doing this for a few hours and you'll have a good start. Once you get down to bare clean cardboard (you'll know when) you get to recover it. I bought a roll of foam backed headliner replacement fabric at Pepboys for $20-30 (I think I had to buy the middle size so it was more than $20) and a can of "special" adhesive for about $7. I bought their adhesive just in case it was special, but it seemed to be about the same as the 3M stuff you can get at Homedepot. I also decided to not re-cut the holes for the grab handles, much cleaner looking IMO.
If you're doing a headliner from a car with sunroof then you'll have to re-cover the sunroof trim panel as well. Probably very similar if not the same process.
HTH