need help to install head unit

need to know the wiring sceme for a 90 gts corolla to install a head unit (eg. power, memory, ext.)

its easier to get a wire harness....i havent seen any around for a rolla though....i would suggest that if u couldnt find a harness (15$usd) then find another corolla harness for newer years and see what colour wires are what...because usually they are labeled

I can help u install it for $30.