Need more info...
SO if the you run with the lights off, everything works OK?
If that is the case I would first look at the wiring for the lights... yes behind the dash, very messy.
I there are some extra stuff installed it frequently is connected there somewhere. Check that wiring out.
Also there is probably a ground screw just behing the panel left of the drivers left foot. Check for wires there that has come undone. Clean grounding pints from corrosion and dirt.. (This can turn into a manual... the chapters on electrical in Haynes or Chilton cover the basics pretty well).
You do not have to 'rewire' but at least fix what is broken... add tape for insulation if insulation is bare or reconnect a connector, a broken wire clamp together...
Judging by your question (no insult intended) but you seem fairly new at the electrical stuff. You need a multimeter, preferably the schematics and some basic knowledge (ohms law etc). If not I suggest getting someone involved with that knowldege (on site...).
Electrical problems ---> usually not hard to fix, but bloody hard to figure out (process of elemination).
Have fun.