Hi Rick.

The outer felts are easily removed once the door panel itself is off.  There is a phillips head screw at each end of the chrome strip on the door's top edge; remove those two screws and the black felt will pop out with a little persuasion (it has several metal clips holding it in, it's obvious once you start).

You can follow this guide, which I used when I rebuilt my window registers.

http://www.corvettemagazine.com/tech-articles/1968-1982-window-regulator-power-rebuild/

As far as the inside felts go, I can't help you there as they came pre-installed on my new door panels.

tinbender... I'm experiencing the same challenge. The "pushin" clips on the outer window felts are anything but "pushin". I'm almost to the point of cutting them off and drilling a few holes and just screwing them in. I just painted my 80, so trying to apply a sufficient amount of pressure to get them to pop in without tearing up the paint is not working. I temporarily have put this project aside in leu of doing a complete brake job. Sorry I can't help...