Squealing leading to the blower not spinning anymore is almost always the bearing on the motor shaft freezing up. Usually because water has gotten in and rusted the bearing. You can remove the blower, and oil the bearing (using 3 in 1 oil, or another NON-scented oil). It will free up and work for a while, but will eventually freeze up again. Check for a leak at the bottom of your windshield. That's usually the culprit.
There are youtube vids showing where to apply the oil. I've done it a few times. It's not hard, and will get you going for a while, at least.
Cheers!
