That answer is true. The resistor is a big (often 20mm square and 75mm long) ceramic core with various sized nichrome wires wrapped around it. All of the speeds (apart from off and high) are derived from combinations of the resistances of these windings. Fortunately, you can rewind the blown winding with an identical thickness nichrome wire of the same number of turns. Any slight variation in thickness and length shouldn't alter the motor speed drastically. Or simply go to a wrecking yard and buy a replacement resistor for your year and model ChevChevy.