Here is my short but sweet DIY headliner tutorial. Please note, I didn't get it perfect as I wound up with a small wrinkle in the back, but if you are better at it than me (or luckier), you shouldn't have any issues.
First off, clean off all the old foam and some of the glue. It should look like this:
Next,lay out the headliner material and be sure it has a little overlap everywhere. Now, fold it in half and be sure to cover all the other half of the material with the new. Alternatively, put a piece of paper between the layers so that the side you will see is covered. You don't want to get any glue on it!
This is the glue I used. Just follow the directions on the can and give both the half of the board and the half of the material that is exposed 2 good coats of it. It shouldn't be runny, but it should be covered. You will need two cans to do the job right, and it cost me $9.99 per can at the local Wal Mart.
Now, I don't have a pic of me doing the next step, but I'll walk you through it. I would advise doing all this on a sturdy table (outside!) as it will let you do this step much easier. There is a reason upholstery guys have tables to work on and not front porch floors! Anyhow, put your hands in the middle at the fold, and work the material out to the edges. Move up, and repeat until you get to the end. If it folds back on itself ( it will), pull the pieces apart GENTLY but firmly. Do this to prevent folds. After you are done, fold the material over and repeat the process. When you are done, it should look like this:
Don't worry about a few hand print depressions. They will come out with a few days in the sun. Anyhow, all you have left to do is trim the edges with some sharp scissors and the upholstery part is done! Now all that is left is to install the board back in the car and enjoy having head room once again!
Here's mine after installation: Note the color is not a good match, but I got 3 yards for $20 after a 40% off coupon at Jo-Ann Fabrics, so I couldn't really complain.