I had my furnace motor start squealing while on the road in 2010 and did a roadside repair: as others have noted, a bit of light oil in the motor bushings fixed it. I removed the furnace and dis-assembled the motor/fan assembly in a parking lot with no more than basic tools. The hardest part was pulling the squirrel-cage fans off the shafts on each end of the motor and then getting the fan housings apart to get at the motor bushings: everything was stuck because it had never been taken apart.
Now I oil the bushings every Spring as part of my pre-season maintenance. Everything comes apart easy becasue I do it every year, and I can have the furnace out, bushings oiled, and furnace re-installed in about an hour: it's quite basic.
