I have a 2000 S-type 3.0. The fabric liner on the front pillars has separated from the backing material (see photos).

How do I remove the pillar covers?

I'm hoping I can just use some 3M Super 77 to reattach the fabric.

 

The pillar covers will pop loose after being gently lifted away with a suitable non-marring trim tool. The cloth was originally attached via a cement being applied to the cloth's foam backing. When the backing breaks down, you get the sagging shown in your pics. You will have to remove the cloth and get rid of the crumbling foam. It will be difficult to obtain a factory look sans foam. Trim shops may stock new liner material with the foam backing, which is the same as used for the headliner.

 

If it helps. This video will show them being popped off.