Headliner conversion kits

Geof, thanks! I think you're right, that I'll be a lot happier with a headliner that's actually made for what I'm trying to do. And since you say you have some experience, I have some follow up questions...

First, I don't understand what my final step will be in the headliner installation. All the tutorials I've read were on cars with trim panels that covered over the edges. My car doesn't have that. My parts car has the trim panels, but it's a 2-door and mine is a 4-door, and I don't think the trim panels can be made to work on my car. My car appears never to have had them. Here's what I have:



See? It's like the original headliner is just magically stuck under that lip. I also keep reading that you should change out your windlace first, and I don't plan to replace mine at all, but I'm not clear on how I will get the sides all in place without making a gluey mess of the windlace.

Furthermore, how do I get the old headliner out from under that lip? Can I turn those little tabs and pull that piece off?