removal
Removing Mk1 rear side windows safely
Wrap a screwdriver in masking tape to protect your paint, open the door, and prize the rear window metal (boomerang shaped) surround from the edge nearest the door first to pop it off the first few clips. You should then be able to pop it all off easily with your fingers. As Ryan said, careful with those clips, I have searched high and low for replacements and cannot find any sources, so you will need to re-use your old clips. You will also need to remove the B-pillar trim too, same as above to remove. Push it from the edge that ‘wraps’ into the inside of the B-pillar.
Once the boomerang surround is off, the rear window is very easy to take out- just ease it out at the top edge, pulling towards you. It will be a bit stubborn at first but will again pop out, chrome trim and all.
When swapping the chrome trim over, I found it easier to slide the bottom edge trim into the window rubber channel first, then ease the longer piece into its channel.
Refiting is a faff – Wind some fairly thin rope around the circumference of the window rubber and rest the window into its aperture. Have an assistant (glamorous) push against the window from the outside as you pull on the rope from inside the car, easing the rubber back over its aperture. Start in the rearmost corner if you can, as its the most difficult bit.
The boomerang piece of trim and the B-pillar trim just clips back in.
From an original post by The Autoad