---First--- Have you checked the fuse in the engine bay and also in the fuse box?
Disconnect the wire harness to the blower motor, I forget if they are pins or blades... Hook a volt meter up to the harness side connector. Turn your key to the RUN position and cycle through the fan speeds and watch your voltage on your meter. If your voltage readings change from Low, med, high switch positions then know the problem is at the blower motor. *note* on HIGH fan speed you should have a FULL 12 volts. If this checks out your problem is probably in the blower motor.
To check the blower motor, Hook a jumper wire up to the GROUND terminal of the blower motor and ground it to a good chassis ground. Then hook up a FUSED jumper wire to the positive terminal and supply power to that wire. If the fan still doesnt work, its definately the blower motor. Now if the blower motor does work.... I would plug everything back together and run yourself an extra ground wire from the ground wire at the fan, if it works now, then you know you have a ground issue.
Hope this helps.