the headliner itself is cardboard with material glued to it. you can new material to cover the cardboard at the fabric store.
the first trim that needs to come off is the front and back metal peices which are metal and attached with screws. next comes the sail panels which have 2 or 3 screws. third is the ones above the doors, which have one screw in the front and the rest are trim clips. these are available used everywhere if yours are broken. last is the metal A pillar trim that has one screw at the bottom in the door jamb. pop those off and you can remove the headliner cardboard.
once its removed you can clean the old crap off the board and use some good spray on(3M) adhesive to attach the new material.