79 rear screen

The rear screen on my 79 Vette is letting water in from somewhere, also when I wash the car with a hose pipe loads of crap comes out from under the chrome screen trim so I was thinking of removing the trim, clean everything up, seal the screen with a bonding agent and replace the chrome trim.
How do I remove the trim without damaging it? I assume there are clips on the body that it attaches to, these will probably be rusted away so are they available to buy from anywhere?
Cheers.