I could have rebuilt it for someone. I did a lot of them. The screws and nuts usually came with most of the kits. I sometimes used nylock nuts on my screws and other times I used the star washer nuts that were supplied.
The coolant fan switch is on the front side of the engine just below the thermostat housing and points at the driver's back. The gauge switch is next to the thermostat housing and stands straight up. The coolant temperature switch (ECM injector control) is the one that screws into the thermostat housing.
When using a meter or test light on the circuit at the fan motor, the fan switch circuit has to be closed or grounded at the engine in order to complete the circuit. If your harness connection is between the ballast and motor, it may be that the ballast is bad. I don't know if the ground runs through the hvac control or not, but probably the hot wire will.
I found this 84 diagram on Pennocks. Maybe it will help.
http://images.fieroforum.com/2011/84-Fiero-Electrical-Diagrams.pdf