Regarding the headliner:
I bought a 73 Dart Sport that needed almost everything. The cardboard headliner was way too warped to leave in place, and it cracked apart during removal. I had to install the replacement, scribe around the opening then remove it to cut out the hole. I used the cutout for the sunroof plug and held it in place with plastic button fasteners. The car wasn't a 100 point restoration, so the deviation from stock wasn't a big deal.