A word of caution: I have had them apart (to rechrome the thin frame around the glass (as these parts´ chrome often looks, if not pitted, at least not very shiny, and have not aged as well as the big frame).
2 issues here: the threads of the small screws are very delicate, and easily damaged. Some of my screws did not come out easily! I did not find a suitable black sealant, in Sweden, to hold the glass in place. They were permanently soft and shiny and just made a mess.
I may have tried new glass and found this to leave a thin, open area....this was many years ago.
So bottom line for me was, don´t mess around with these vent windows!
New thich seals, by all means. They fit superbly. And clean and lubricate the opening mechanisms. They are fragile in the weak, cast (crappy metal) mounts, where the rigid pin of the vent window goes. The U shaped opening often needs to be pryed open a bit, in order for the pin to slide in. Rubber hammer was needed in most cases.
Peder