Are all your instrument lights out? Did you check your dimmer, maybe it is turned all the way off?
I seem to have the same problem with the my gas gauge. I replaced my sending unit, cause it was so plugged up. The gas gauge still did not work after installing the new sending unit. Could be just a dead gauge.
As for the instrument lights. Looks like at least 1 doz. #194 bulbs, these are good to have around, many uses for these bulbs.
You didn't mention what model or year truck you have. In my 1972 repair manual it list the bulb types, but not how many you need.
Most likely, you will need to take the instrument cluster apart and go from there.
The manual lists a conventional cab, a P-model, and a F/F Cowl.
It does not elaborate, how to tell the difference between the models.
Hope this info helps. Good luck