Leak in rear window

I'm having a leak-water problem with my 1964 4- door Valiant. We believe that water is coming in around the rear window and this results in standing water in the trunk and the carpets in the back seat on the passenger side are wet. I am going to remove the back window and trim. I have a few questions:
1. To take off the trim around the window , I know there are clips holding the trim on. Can anyone tell me how this is done? Tools? I have read some articles on the Web but any help would be helpful.
2. Can the clips be reused on re-install of the new Window Gasket?
3. If not does anyone know where I can buy new ones.

Thanks Valiant 64.