A headliner is one of the easiest things to replace for just about anybody with the use of two hands.
You remove the trim that holds it in place, and will probably have to remove one of the front seats. after getting the headliner out you tear off the old junk, and use a wire brush to remove the remaining crusty funk that is left behind. Once the surface of the backer is all clean, and free of the remaining dust from the old headliner, you go to either a fabric supply store (to include Walmarts' fabric department) or an automotive upholstery supply store and buy enough replacement, foam backed, headliner material to cover it.
Then laying that backerboard on a clean surface (like a garage floor, but not like MY garage floor) you rough cut the material to leave a 3" or so overlap.
Fold it in half, on top of itself leaving it in place over the backer board you intend to recover. .
When you went to Walmart, you should have also bought a can of 3M Super 77 spray adhesive.
The nozzle has an adjustable spray pattern, (L.M.H.) I choose H.
Spray the adhesive on the backerboard, and the half of the back of the material and give it 5 minutes to tack up.
Then.....
Starting at the middle, with your fingers, start pushing the fabric from the folded center onto the backerboard, I move my hand back and forth across the crease as I push the fabric onto the backer board being careful not to let the rest of that thing flip over onto the backer until it gets to the end.
Then, once that side is done, repeat the same for the other.
Whip out a brand new single edge razor blade, and (using the sharp end) cut the remaining overlap even w/ the edge of the backer board.
So easy even a simpleton w/ less than a sixth grade education, a can of spray glue, and a razorblade can do his own headliner.