||Pull all trim loose from around the headliner, you know all that lovely grey plastic interior accoutrements.
||Unbolt the sunvisors, if the headliner is falling then chances are the visors are toast too. Plus they have to come out so you can remove the board. Be careful on the passenger side if you have a lighted vanity mirror, its wire run up through the board. You will undo the wire AFTER you drop the board.
||Undo the interior light in the center of the headliner. On a T-Top you won't have one just the two in the back side panels. You will slide the light thru the hole when you drop the board. Just let it hang, it will be fine.
||Now to get the board out... This is the most tricky part and if you screw up you will either break the board or scar it up to the point of being unusable. This is all written assuming you have a car with a whole roof and no t-tops, if you have t-tops pull them out to give yourself more room and this will all be much easier. Slide your seats back all the way back, and recline them as far as you can. Tilt your wheel all the way up. Put the emergency brake on and pull the floor shifter all the way down into low. This is all done in order to give you the most possible room to rotate the board. Have both doors open and see if you can get a friend to help you maneuver the board out of the car. You must take it out the passenger side, it won't clear the wheel on the driver side.
||It may look like there is no way it'll ever come out. But it went in that way, it'll come out that way. Drop the front of the board down a little and rotate the front so it comes out first. You will want the passenger side up against the roof and the driver side against the floor. Now you will see why getting the seats and shifter back, and the wheel up are so important. Make sure the board goes over the shifter not under it or it will bind. Play with it a little and it should come right out. But if you put to much force on it, like if its in a bind you'll break it. And if you don't watch the edges they will get all bunged up when you're pulling it out, so be careful.
||Now lets assume you get the thing out without ruining it. First peel the old material off, for the most part it is always ok. Then you will see the culprit. The old foam backing on the material has broken down and turned to powder, so the headliner falls away from the board. Scrape all the old foam backing off the board with a wire brush. Do this outside since this junk gets everywhere. Once the board is clean fix any nicks, holes, or developing cracks in the board with aluminum tape or something of that nature which will lend some strength, shape, and will stick.
||Now you have to get the material. This stuff is cheap even for the good stuff expect around $12.00 a yard, and probably need around 1 1/2 yds to be on the safe side. A t-top car uses the same ammount of material, just more is wasted. Just take in a small piece of the headliner preferably somewhere that was under some trim so the color won't have faded down any. Any competent shop should be able to get close and they should have it on hand. The material in use today is better quality than that which was in the car originally. In most cases they will also have the glue you will need also. We always used Vinyl Top glue which we sprayed out of a paint gun. It is strong as nails and works great for putting on the headliners . But there are several brands of spray trim adhesive such as 3M which are designed for headliners that you can use. But make sure that you only use good materials cause if you don't you'll be doing it over soon enough.
||Spray the board with your adhesive, and then the foam backing of the headliner. Let them sit a second to tack up and slam em' together. Work from the center out. When you get to the indentations for the front seat belt mounts carefully work the material into the holes and don't stretch the stuff too much. You may want to do a dry run of this before you start in with the glue. Let it dry for awhile and then trim around the edges and the holes with a fresh razor blade. When this is all done you can reverse your process and reinstall the headliner.
||Now if the side panels in the back are bad re-do them in the same manner as the headliner board. If your sunvisors are whipped you will probably want to take it to a professional, especially if it has the lighted vanity mirror. There are so many things that can go wrong with the visors I don't recommend messing with them.
||Now you should be back in the car with a new headliner and the like. Put in all the trim and Viola! You did it! As a note about this. The most consuming part of this is the labor of taking it out and cleaning it. Talk to your trim shop and get a price if you just drop off the board and or visors to be covered. You may find out this is a deal you can't pass up since at least 50% of the of of the job normally is labor.