remove the front seats and the rear seat bottom cushion
remove A, B and C pillar trim
unscrew and remove the domelight, the sunvisors and the clips, and the Jesus bars
you need an automotive panel button popper tool to lightly pry off the buttons, I use some plastic to spread out the prying force under where the tool hits the foam, so it won't get crushed.
get someone to help hold it as it comes off and don't crease it, wiggle it out (probably) out the back door if it's a sedan.
look for an auto trimmer in the phone book in your city, they will have the headliner material for a recover and the proper contact cement(any other glue will not hold) It's just easier to have them recover it, as it only takes about 20 minutes, and half that is dry time, and they have the glue sprayer set up, I don't even clean my sprayers, it's impossible, I have to toss them.
install in reverse order. don't press down hard on it with your fingers when putting it up, and don't crease it. I also constantly make sure my hands are clean, so I don't get fingerprints on it.