There are two things on that page, the blower ressitor that controls the fan speeds below max. and then repairing the blower motor itself. If your motor's brushes are worn down to nubs, the motor will run slower and slower (on all speeds) until it finally stops moving. Try taking your motor out, clean and inspect it, lube up the bushings and clean the fan blades, as noted on the page:

http://www.4crawler.com/4x4/CheapTricks/Blower.shtml#MotorRepair

Then while the fan is out, clean out the ducting and see if there is anything obstructing the air flow.