One other thing to check before you condemn the fan motor is to verify the ground. The fan is grounded on the top forward belhousing bolt (where the transmission bolts to the engine, drivers side, top frontmost bellhousing bolt), just make sure that wire there is tight and not corroded.
The fan motor can be serviced separately, but the complete asssembly must be removed (fan, motor, and shroud). The assembly can be removed by taking out a single bolt at the bottom passenger side of the rad and unplugging the electrical connector. The rest of the shroud is retained by slots and is easily removed. Once you have the complete assembly out you will see that there is a clip in the center of the fan, remove this clip and drive the motor shaft out of the center of the fan with a punch. When the fan blades are removed you can see the 3 bolts that hold the motor to the shroud. Remove those 3 bolts and there you go... Assemble in the reverse order with a new motor(available @ any car parts store). Some times it can be extremely difficult to get the fan off without damaging it, so you may just wanna do as thewickedjester suggested, and just replace the complete assembly with a used one. Good luck.
