I've done a couple headliners and if it's a one-piece board then not too bad of job. Have a helper or get some bungee cords. Remove it, use bungee cords to support it so it doesn't collapse while removing the trim, gently clean with bristle brush, blow off debris, size out the headliner, leave a good couple inches or so extra for overlap, spray adhesive 3M 38808 on both board and cloth, let set for about 10 minutes, grab a helper, CAREFULLY lay down so as not to create ripples, then fold over edges, trim excess if needed. Hard part is the install. Use bungee cords like in the video to support the board again for install while you work the trim screws. Hardest part is finding all the trim screw holes because of the thickness of new headliner. Have lots of patience.
Good vids:
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