If you have what appears to be the low speed, that may just be the air recirc. door opening due to a non-functional door solenoid. It is uncommon for only the middle speed not to work, since the failure of a blown thermal fuse is that only the top blower fan speed works.
The resistor pack is located beneath the plastic cowl cover behind the firewall in the engine compartment. Four or five screws to remove the cowl, and two screws to remove the pack, and a connector. The pack sits on top of the heater fan box. Just look for a plate held in with two screws and a wiring connector. Once removed, you'll see two or three coiled wires and a thermal fuse mounted on the other side. The thermal fuse is the culprit.
A) Repair with a 291.2 degree F (144 degree C) thermal fuse. (Radio Shack part #270-1322a or newer #270-1320). Don't solder it in. It MUST be crimped in, or the heat from soldering it will blow the resistor. You can cut the body of the old fuse off and twisted the leads of the new one to the leads of the old one. All speeds to the blower should work after this repair.
B) Solder in series a 10 amp fast blow fuse.