I would check everthing you can before changing the heater motor as you have to take the dash out to change that!
Start with Fuse!
Then the heater resistor which is by the off side headlamp and has 3 wires going to it, they go rust and fail.
Then check the 3 speed control knob on the dash, start with the plug on the back as these melt.
MrMPuk
February 2007