Wiring Nightmare

[91WHT240sx]

About 2 months ago a purchased a car, my 91 240sx. It has some issues to be worked out of it. List of wiring problems: my speedometer or overhead display does not work. thinkin maybe VSS. also my windshield wipers go on every time i hit the brakes or turn on the turn signal, and sometimes they will just go on out of nowhere with the wipers even off. If i dont start my car before i turn on the headlights the gauge lights do not work. the odometer works intermitently. Please help my wiring possed 240.