There may be a simpler problem,, I assume the for speeds are low, med-low, med-hi and High and the one speed that works is high, right. The other 3 speeds are not working?
Before you check the fairly expensive control module, locate the resistor and check it, This will be a device with 4 wires goign to it that is attached to one of the air paths, Very likely on the outside of the firewall (But possibly inside) it Upon removal of the device (Detach the 4 wire-connector, remove two screws) you will see a coil of wire, odds are there is a break in one of the wires, Replacements are inexpensive and you already know how to reassemble (reverse of dissassembly) Trick is knowing which device is the resistor... I've seen enough of them to know, but I can not describe it other than to say it's a metal plate about an inch wide by 3-4 inches long, screw at each end, and as noted, 4 wires, one for each speed, One or two of the terminals (usually the end ones) may have two wires hooked to a single connector.
Note if the only working speed is NOT high (IE If it's low) then this part is not bad