Replacing Rear Side Marker Lights

[twotees]

I'm trying to replace the bulb in the left rear side marker housing. I understand from other forums that to access the bulb one has to pull away the outer fender panel. I also understand that the several screws attaching the panel to the body have to be removed. I have done that, but the panel does not seem to want to peel away as easily as the other forums suggest it should. The top left portion of the panel seems firmly secured to the body, even though one can insert a screw driver or broad flat knife all around the edge, even between the lower panel and the one above it. What is restraining the panel and how can I get it to peel away without breaking it? Is it secured by some plastic plug as so many other parts of the car are? Often those others have needed to be tugged quite hard before popping loose. In this case I'm reluctant to pull it too hard without knowing what's restraining the panel. Thanks.