Easiest way is to remove the chrome first, then cut off the outside flap of the old window gasket along one width and one height. The window then pops out easily.
Remove all old w/s gasket
Clean and rustproof the metal frame.
Buy a new w/s gasket...call an auto glass guy to install, he will use all the proper professional sealants. (costs $50)
You will probably find that the clips thathold the back edge of the air intake panel will be rusted, you will need to get some (7 needed?) They need to be caulked and installed, under the gasket.
If your dash is cracked, this is the time to install a dash cap.
What I did....
Elio