I lost my dash lights on my 87 GT and about 100 miles later I lost my turn signals. Headlights, taillights, and foglights all work fine but everyone I talked to said I needed to change the voltage regulator on the back of the instrumant cluster.
The people you talked to are uninformed. The IVR is there to regulate and create hystersis in the gauges.
If you lost the dash lights, run your dimmer up and down a few times in case you have a dead spot. Check Fuse 13. Then remove the switch and measure in/outs if nothing else was the cause. It sounds like a dimmer issue.
The turn signals might be a coincidence. Do the hazards work?