I have a DVD deck, an amplifier, and a sub woofer. I took my Nitro to Best Buy to set up an installation appointment. I was expecting to pay around $300, which includes the wiring kit. I was a little surprised that apparently I need a special wiring harness for Chrysler vehicles which costs $150. I asked what the purpose of this thing was and why I need it, and he tells me it's because if Chrysler needs to run a diagnostic check on my Nitro, and I don't have it, they won't be able to do it without this $150 harness. My question is do I really NEED this harness or will another one do?