Hopefully the gasket will be reusable but you will have to evaluate that after you've tried. Some of the reproductions have been reported as not fitting well so it may be worth the effort.
Basically you just reverse the installation
- Remove the molding removed the interior trim where you can.
- Have a flat smooth tool like a flat plain metal spoon (your going to use the handle end) or a glass tool (often a white nylon tool) to work the corners and edges. Along with this you will need a thick cotton or nylon rope section (some will use a heavy duty extension cord)
- Place the cord or rope around and in the inside lip of the weatherstrip. This should reduce the grab effect of the gasket to the body while you work on other sections
- Corners are the most difficult and you will need to provide a consent, light amount of outward pressure. Take it slow and try to keep from producing any sharp bends or folds while you work back and forth on both sides and the edges on one of the corner while keeping up the light outward pressure. . This is when weather strip cracks or tears
- Once you get half of the gasket unseated the window should slide up or down from the out side and lift out.
This is all from memory so may have over looked something but can't think of any more - without being there leanding a hand