You want to reupholster the headliner? I have a 95coupe I didn't take off the headliner when I did my interior I just dyed it from inside. But I did take off every other plastic piece available on the car. I'd say take that all off first then just pull on it really hard because it probably has those pegs that line up into holes in the roof, just like in the door panels.

If you figure it out let me know because I was planning on reupholstering the headliner at somepoint in time with some kind design myself aswell.

As for the weather stripping I used vinyl dye on them. Their like a rubber material. I used vinyl dye on everything actually. Clean them very thoroughly because they will be full of grime even if you don't see it. I put a ton of coats on them and let them dry for a couple of days I put them in too early once and some spots came off from the doors closing on them. I'm not sure what other products out their are good for rubber but I tried the dye and it worked pretty well. They were tan and I dyed them black so it was an extreme color change