I would suggest taking the cover off the plenum,(oblong cover with two hoses and six screws at the base of drivers side windshield) there is also a sensor that twists out. Below that the air filter, and below that the blower and regulator mounted on the blower.
They both can go bad, if the fan spins it is probably the regulator, if it does not spin freely there is probably corrosion on the bearing/shaft. The regulator sits in the ground side of the motor the other side is hot. You can get the motor and regulator on Fast Lane right here, and ther is a DYI Article