Not quite having got over the shock of what a replacement costs, I decided to tackle this myself. If you are not comfortable with the girlie parts....buy one. But let me tell you, there is nothing girlie about waiting outside of JoAnn Fabrics at 9:48 on a Sunday morning in a lifted Ram with 33s if it means I won't have to stare at staples and a saggy headliner.
You will need two yards of your choice of fabric at least 48 inches wide and a can of spray adhesive that is compatible with PVC ( that's the foam in the headliner shell). I chose a nice brushed black denim because it would contrast nicely with the gray interior and it was on sale....( got that from my Mommy..). Paid $16 for the denim and $10 for the adhesive. I ended up with a couple of small wrinkles in the corners because the denim was a bit stiff ( not enough to matter to me). You might find a flannel or a knit would be easier to smooth in. Be extra sure to make manly man jokes with the counter ladies about being secure enough in yourself to buy fabric without the wife or play the "Dumb Man" part if you think it'll really get you somewhere ( leave the ring in the ashtray if you're serious though).
Back in the shop, start by stripping down the sun visors, clips,lights, console and grab bars etc. Put all the hardware in a cup or tape it to whatever you took down. Don't throw them somewhere like I did...Pull down the shell and get it somewhere with room to work.
Peel off the old headliner,being careful not to take the foam with it.
Start at the bed side of the shell and spray glue from door to door about a foot wide NO MORE!! Spray a foot wide ON THE BACKSIDE of the fabric. Wait a minute for it to "tack". Lay the rest of the material in the middle of the shell and start laying it in glue to glue. Work out as many of the wrinkles as you can. Lift and stretch-pinch and poke...whatever it takes but work fast. Lay the material back and do another foot.
When you get to the edges,trim any excess off but leave around an inch and a half to overlap (underlap???) between the shell and roof. Work one side at a time. On the straight runs you can just spray glue on both sides and fold it over, but on the curved parts, you'll need to make darts ( little arrow cuts) so you can make the corner. KEEP THE DARTS 1/2" OR SO FROM THE SHELL EDGE or it will show. Go relax a bit and be thankful that's over.
Back to work. Cut out any of the openings leaving 3/8" to the inside. I just cut slots for the little ones. Start putting it back together. I did the quarter post trims first to hold it up,then the console,then the dome light,finally the visors and the clips. I had forgotten to replace the little nylon blocks on the passenger grab bar so it'll be fun to watch the wife get in without it....I ain't going through all that again just for that one bar.
All in all...for $30 and two hours...I'm very happy.