Are you thinking custom or aftermarket or just want an OEM replacement? The headliners I have done were simply pull the seatbelt plastics and some other misc things off. Jam a screw driver between the current headliner and the roof and pull it out. Then take your replacement and snap it in, along with the other things that you removed. I have never done a GM car so perhaps they are different. Good luck!
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Originally Posted by JustMiata
It's like this: The toadstool juice fires through the unicorn injector into the fairy dust chamber, where the tiny wizard does his secret work...Then a gang of keebler elves get hopped up on the crystalline byproduct of the wizard's tinkering, (they smoke it) and then the elves push the spinning triangle through a series of dimensional portals to a final realm codenamed the "exhaust port..." At least that's my undersanding of rotary sorcery...