[98FireyGT!]

Sounds like you should get a used Mach 460 deck and reinstall it to me. You can usually get on from ebay for around 25 bucks.

+1

Though if you really want the aftermarket deck AFAIK walmart sells a Scosche wiring harness that will work with the 460 system. I kept my Mach system entirely stock though I added two 10" Kicker Impulses in the trunk and just spliced a line out converter into the signal wires BEFORE the amps. Took about 10 minutes to set up and it retains a nice stock appearance.

As for the keyless entry/dome light problems, I would strongly suspect your son jacked something up cutting and splicing the wires. I would wire everything back to stock and then just leave it alone.