Window winder

Had the same trouble in a new van Just put a new winder in it Easiest fix and not expensive.You could try some silicone spray but NOT WD 40.

If the Princeton has the lightweight Camec windows (very common).....as Tom says, easy to renew...not expensive.
Would be worth giving the winder boxes a good drubbing in silicone spray first though.....I buy a pure food grade silicone spray from cheap shops ($7)...no worries about what it gets onto......you might be able to wash dust out with that, by squirting it in through the strut slot, via the supplied tube on the sprayer.
Replaced one of my winder boxes a couple of years back....as I recall, from the inside you'll find some countersunk screws buried in a shallow groove on the window frame. Once you screw these out, the winder box comes free (again, as I recall :-). The window strut stays in the box mechanism, so to get the perspex panel free of the winder assembly, I had to drill out the pop rivet connecting the strut to the perspex panel's frame. Good luck with it.

Thanks to everyone for their suggestions and comments. Will give them all a try and let you know the outcome.

Cheers