Truck Repair: chevy electrical, chevy silverado, gas gauge

Question
hello.  i have a 1989 chevy silverado with a 350 engine, automatic transmission, 257K miles, fuel injection, and cruise with tilt steering.  i bought a truck knowing that every once in a while, the dash lights would go out when the head lights were turned on. once in a while turned into often, and now the dash lights go out anytime the headlights or parking lights are turned on.  also, when the dash lights go out, the temp gauge goes all the way up, and the gas gauge and oil pressure gauge go all the way down.  after some time, a clicking noise developed and my parking lights would come on when i hit my brakes unless i had the headlights/parking lights on, in which case the tail lights and brake lights just wouldn't work at all.  i checked the fuses and a couple were blown, but each time i replaced them they would quickly blow again.
the problem progressed to where the tail lights and brake lights wouldn't work no matter what and the fuses stopped blowing.  the clicking noise turned out to be a bad flasher, so i replaced it and i'm back to where the brake lights work when the lights are off, and no brake lights or tail lights work when the lights are on.
also, i disconnected the dimmer swith and the gauges stopped messing up when i turned the lights on.  i'm pretty auto-mechanically impaired so i don't know what to do from here and if this is something common and easy to correct it would be fantastic
thank you so much for your time  

Answer
Those are classic symptoms of a bad ground connection.
Up above the parking brake lever should be a ground block. Make sure all the wires are clean and tight.
Look for where as many of them as you can see connect, and make sure they are also clean and tight on the other end.

Van