I have a 2001 National Surf Side and my fan motor was squealing badly. I took it to my mechanic and watched him remove it from under the dash on the passenger side, took him about 3 minutes as there were only 4 screws holding it on. He ordered a new motor and then removed the squirrel cage fan from the old motor, put it on the new motor and re-installed it under the dash all of which took maybe 10 mins.
The other thing it could be is the fan switch, perhaps it has gone bad.
Hope that helps
2001 Fleetwood Discovery 38F, 2013 Honda CR-V, Roadmaster Falcon All Terrain Tow bar. Magalia, CA, iRV2 Supporter, Member FMCA