Is this a true Astroroof or the ASC roof? Before you remove anything, make sure you check and see if the delicate backer board is there... My Astro car has the board, my ASC car did not (it does now).
Also, to make things easier on yourself, I'd recommend pulling the front seats. All you need is a 13mm socket and a few minutes. The headliner will be very fragile and flimsy especially with that big hole cut out of it. You want to be super careful when handling it.