Hi,
I would also like to know about windscreen availability for when the time comes.
But in regards to the window, i would buy a whole new motor, you can do a DIY on it and clean it up and it may come good but it's only a matter of time before it fails again. I would try sourcing them from Japan or eBay, not sure if there would be a difference between the G35 and V35 motor, just as long as you buy the passenger side one if it's off a G35.