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Typically when your tail lights and dash lights both don't work at the same time it us usually a problem with the rheostat. Normally the rheostat causes a short and blows the fuse, but sometimes it just doesn't contact. Have you checked the wiring that runs down the driver's side rocker panel? It should be a brown wire that has 12v with the headlight switch on. Do you have working license plate lights?
I don't have a diagram that shows where the fusible link is and I can't remember from memory. I can tell you that the fusible link is on the black wire with an orange stripe. If you check for 12 volts at the black with orange stripe wire at the main light switch it will tell you if the fusible link is bad.
Here are some diagrams showing how all of the dash panels and parts are removed. Let me know if this will work, there isn't a whole lot published on these trucks anymore. I guess they are considering 1991 vehicles old now.
Sometimes they get jammed up. Push in on the stem, push the button and then pull out. Sometimes you have to wiggle and jiggle it back and forth a little to get it to release.