To answer what turns out to be the original question, remove the chrome trim by gently prying from underneath. If it's a coupe, the place I found easiest is at the inflection point above the rear side windows. Roll them outwards from below. They hook on where the roof panel edge has a lip on the top, and clip under the lip from the side panels.
The second question we all ran away with - the roof and side panels are spot welded, then the channel above is filled with a putty that hardens. If repainting the car, you may already need to chisel this stuff out and refill it because it cracks over time and lets water get under it. Use a large flat screwdriver and wire brush or wheel. You'll see the spot welds when you get the filler out.