removing trim and boot snaps

How does the trim on the top of the doors and below the quarter windows come off? I tried removing the small piece below the quarter window but can't figure it out. There is a metal clip on the front and in the middle of the trim piece but there is something different on the back. Looking at the bottom side with a mirror, I can see threads from a screw sticking down. The front convertible molding also slides under that trim piece. I don't want to break anything.

Also, the convert boot snaps need to be unscrewed so I can removed the trim around the base of the top. The screws just spin and don't come out. Is there any way of getting inside the area to hold the clips from spinning...or do I need to start drilling out all the screws? Thanks