I own an 88 chevy K5 and I need to remove the vent window so I can install a new weather strip. I removed all of the screws on the door panel and popped out the plastic plugs but the very top section of the panel is giving me trouble. it will not pull off. It appears to be clamped down with a door window seal where the window hugs . I dont want to force it off without finding out how it is held down What is the trick?