Alan,
If not hard as a brick, you would probably need to get the gasket heated up (heat gun) to make it flexible, and then slowly work the glass out. It probably will take two people. One to pull the seals lip back while the other pushes the glass out.
Honestly, they do repop the 67 front gasket now. I'd just cut it out. Not sure the 30-50 you might get for it after is worth the possibility of breaking the glass and the time and effort trying to save it.
