Today, the headliner is attached onto a plastic tack strip about 1/8th of an inch thick. The strips used around the windows are help in place by rivets. While the job is not real difficult it does require a lot of patience and the ability to work in a lot of uncomfortable positions.
I spaced the rivets about every 4 inches, and used a clamp, where possible, to help hold the tack strip in place. My learning curve is SLOW so it did take a little experimenting to develop an efficient method for drilling the holes so the tack strip didn't have any bulges.
I replaced all my tack strip, even though I could have had my upholster do it. The job is time consuming and I wanted to save some money, and liked the challenge of figuring out how to do it. I probably have over 8 hours of work in removing the old tack strip and installing the new.
Good luck, Mike