I've taken all of mine out and refurbished them. They're in primer awaiting wood graining. They just lift off after taking all the crews out. It may feel attached by something else, but it's probably just stuck from rust or something. At least this is the way I did it on my S-11.
Do be sure to keep the screws in jars or something. Photograph the vent window handle mechanism and the upper pivot bar and any other part that comes off before taking them apart. You know, how the vent handle springs are kept in place and stuff like that. You're going to need this photo reference when you go to put them back together.
There is a fuzzy on the garnish moldings along the lower edge to protect the window when its rolled up and down. That will need to be replaced, and there is a thread about methods to do this somewhere on this site.
I sandblasted the garnish moldings with a fine sand and then hand-sanded them with yellow sanding pads. 180 at first and then 220. Tap out any dents. You can sand out scratches that are not too deep with a more aggressive sandpaper weight. Any larger dents I tapped out with a piece of steel coming in from the inside inside of the frame. Then finish sand it on the outside. If you have to, fill whatever cannot be smoothed out. I had to get another frame from a salvage yard. Mine was too rusted on the inside.
Then primed them. It's a toss-up where to replace the fuzzy strips before you paint the moldings or after. I wanted to get everything primed first and deal with the fuzzies later.