hey guys please let me know what your thoughts are on this issue i have with my 02 cavalier:

We bought it last year and the guy had not used the correct harness to install an aftermarket radio. He had a wire going to the ignition coil and it was somehow tied to the radio and you also had to connect these two wires together in order to tun the radio off after teh car turned off. I replaced the stereo he had and wanted to get aharness but wasnt sure i needed to spend the money... i bought alitle switch and put it on the cable to turn on off andi cant rememebr exactly how it was set up but i changed it so that it turned it on and off. After a a little while, when the radio was turned on while driving the car would bring about all the lights on the dash board with the theft system and the milage would say error... it would come back though after you turned the radio off... so we decided to do without turnin the radio on at all and all seemed well. Until a few days ago when i decided to turn the radio on,, it did the same theft system thing and i turned the radio off and it went away. the next day the car wouldnt start, after tryuing it so mny times IT WOuld start but the Theft sytem/ fault lite would be on and all gauges would be down... you cant put it in gear.

What i want to know is, is the radio issue causing this? Will i have to take it io a dealership to have the theft system reset?
Can i just take teh radio off alltogether and go back to working state without it? the previous owner had all kinds of wires hangin or rigged up where the latch to open the hood it and a few fuses taped together with tires goind osmewhere?!?!? can someone tell me what wire i should disconect to make things go back to normal?