Just one thing about TopNotch's link to the ALDL and retrieving codes. The ALDL connector is used in several GM applications and is usually mounted underneath the dash in the position shown in the link. On the Fiero, it is mounted upside down, so the A and B terminals will be on the bottom row, passenger side of the ALDL. A small paper clip straightened then folded into a U will work well when inserted into the A and B terminals. Be sure the ignition is in the OFF position when inserting and removing.
Donster sells some good ground cables that may also be of some benefit with the dim lights. Have you confirmed that the thumb wheel underneath the light switch is rolled upward? Roll it until you feel resistance. If you roll it beyond the resistance, it will click into an Interior Lights On position and if you have your doors open at the time, you might close up the car and drain the battery. So close your doors when you test it.,
Have you tried grabbing the round piece that surrounds the hazard light button and pulling real hard? The tendency is to press the button to make it release, but the Fiero hazard button doesn't work that way.