My driver side window is stuck down

Most likely it's the very stiff lube and crud making the motor think the window is fully up. Can you get it into a warm area to let it thaw out? Even using something like a hair drier blowing into the door might be enough to make it free up. If not and you don't want to work in the cold then most shops or a dealer could repair it. They would let it warm up and then probably replace the regulator assembly and lube the glass tracks in the door.
Personally if I didn't have a warm place to work on it, I wouldn't, you need to remove plastic trim and the glass and in the cold it is real easy to damage them.