I went to Lowes and got some 3M spray adhesive (like $8) and then to Hancock Fabrics and I got ..something.. Gray headliner material ($15 for 2 yards) I took a sample of my existing saggy liner with me that I pulled from under the edge trim so it was as dark or nearly so as factory, it's VERY close the stuff I got, it might be a shade off, but it looks damn good to me, less than $25 and an hour or so of my time later and here you go:
That's right after I put it back in, those finger dents are pretty much completely gone after a couple hours and it's smooth now, still looks great several months later.
Take off the trim, take out the headliner (it helps to have a 2nd pair of hands) scrape off all the crud, apply 3m in a nice even coat, put down the liner and mooth it, trim it with a razor/scissors to the edge of the backing material, and rehang it and put the trim back on, all told less than 2 hours of my time, I could do it again in under an hour easy now that I know how that fracking trim comes off.