I'm facing the same issue. I went and bought an ebay headliner that does not have any plastic trim on.

The show-stopper for me last weekend was the front. There are no teeth in the front (and no plastic strip on my headliner), just a long strip of metal about 1/2 inch wide (not the trim pieces) held on with many sheet metal screws. It seems I need to start up there and screw the headliner under this metal strip. I stopped when I saw that if I did not get this part perfect the rest would look even worse. If I start at the back, I won't be able to get to the screws that the headliner needs to tuck under. I can post pictures, but I'm stuck!

Thanks, Richard