You'll need to take the front and rear windows out to do it right. It's kind of a PITA and hard to get it tight unless you know what you're doing. I did my 67 notchback Barracuda and it came out only OK. I should have farmed it out!
Headliners are cheap considering farming it out. You could probably screw 2 of them up and still be under the cost of a pro to do it. I did mine and turned out great!!! Just take your time.
If you do it yourself I recommend buy the headliner from Legendary interiors. I bought a made in "usa" headliner for $65 on line and spent way too much time installing it. Only to take it back out and then buy one from legendary. It fit 10x better and went a lot smoother. It was also nearly 3x the price. If you can get someone to do for 2 or 3 hundred dollars then have them do it. Just my opinion. I have done 3 of them and they are a pita!
First I bought ( from PUI ) was wrong too. Year One was able to get another here in 48 hours that was perfect fit and about the same price.
Replacement from PUI arrived 12 days later.