In addition to the great pics and instructions by EdChapman...
Here's how I did mine on my 87 GN.
Disconnect the battery so you don't blow a fuse messing with the dome light.
Remove the front headliner trim the one metal one. You may need to go to your local Buick dealer to buy new clips. With a screwdriver, you may be able to remove the clips without damaging them.
Remove the coat hooks and the front sun visors.
Remove the front two plastic A-piller covers.
Remove the passenger and driver headliner trim (the metal ones above the window). [Note the position of the metal trim to the plastic trim (front and rear) prior to removal.]
These can be removed without a screwdriver and usually without breaking them. The plastic clips are held by a phillips screw. They are puposely loose. Do not tighten during reinstallation. You may have to adjust their fit up reinstallation, but do not torque them down.
Remove the plastic door trim. Also pop out the plastic trim that surrounds the rear quarter windows. there is a hidden phillips screw there on each side.
Remove the dome light. Clean or replace as necessary. My dome light fixture required a repolish.
You don't have to remove the rear window trim. You should be able to remove the headliner. Do not break the foam headliner. Do not remove the fabric until it's out of the car. Breathing that old foam isn't fun.
It's easiest to remove the entire headliner from the passenger side with the window rolled down.
At this point you may have those lead sound deadening pieces coming off. Use automotive trim adheasive to re-install.
Strip the fabric off. Use a wire brush to remove the old foam. Be diligent but do not damage the foam. Do not crack the foam board. If you do, use duct tape to repair.
Apply adhesive to the foam board as well as the new headliner fabric. Apply headliner fabric (preferable start on one side and apply without inducing wrinkles) in one entire piece to the foam board. Do not "paint" the glue onto the headliner. It's best to use an areosole. Be liberal with the aerosole.
Once applied, smooth out any wrinkles in the headliner using a CLEAN 6" ruler or your clean hand. Use an Exato knife or razor blade cut a very small "X" for the visor holes. Use chalk to mark where the coat hook holes will be.
Cut appropriate hole (not bigger than the one found in the foam board) for dome light.
Let dry for a few hours. Trim headliner, but you may want to leave 1/2" or 1/4" overhang in case you end up being short somewhere.
Install headliner from passenger side. Insert headliner into the rear metal window trim. This may require two people so it doesn't drop. Use the plastic clips in the door area as they will hold the headliner up.
Square the headliner into position. Note the holes for the coat hooks. Raise the plastic rear quater window trim and install.
Check that headliner is square into position.
Check that when installing dome light hardware the headliner is square into position (use the old holes as a guide). But you don't have to install all of it until the end.
Install front metal windshield headliner trim.
Once the visors are installed, you have lost the ability to square the headliner.
Now you can install the dome light, but you can leave the cover off until the very end.
Check to see if dome light is working by temporarily re-connecting the battery power. It would be pain to find out you accidentally caused the dome light to malfunction.
Install visors. Use existing hole. You may have to use a drill or punch small holes in the fabric to reinstall the visor phillips screws.
Install front A-piller trim.
Install coat hooks. I had to puch a small hole for the screws in the headliner.
Install plastic rear door trim do not torque the phillips all the way...yet.
Install metal trim driver side and passenger side front windows. Note the position of the metal trim to the plastic trim (front and rear) prior to removal.
Now after adjustments are made, torque phillips screws holding the plastic door trim.
The order in which I re-installed the trim pieces is a guideline. Use your own judgement if you feel another way works better.
