I want to install a different deck in my grand am but when i went to buy a harness the guy at the counter told me i needed to order a speciaal on or else disconnecting the factory deck will trigger the security feature and my car wont start anymore. Is this true? is that the only way to hook it up?

He may be confused with needing to retain the chime module. All system chimes are played through the factory stereo system. This item here allows you to install a non-OEM stereo and still retain the factory chimes...

CRUX SOCGM-17 GM Factory Integration Interface Retains the door chimes and audible warning system in select GM vehicles at Crutchfield.com

if you dont have onstar and that all you loose is the noise. so if you dont care about the dingers you can get a cheap harness adapter and if you wire the keyed power wire to the rap circuit somewhere it will function as the original did

awesome.. so it has nothing to do with the security then?
Also, i noticed then amp is also factory, if i would leave the deck and just hook up another sub and amp would that be too much for the battery/alternator?

the only "security" there is which i think ended before your year is the radio theft lock which should be turned off before you take the radio out or it will lock up. this is only the ones that have the little led. if you have the one after that save the oem radio to put back in when you sell the car because no one will be able to use it anyway. as far as the sub/amp to many variables on what you are going to use. the battery isnt that great neither is the alt for being designed for excess power. my 03 monte i had a battery 100cca over stock, used 2awg power and ground to a 800w sub amp and 400w highs amp. the lights dimmed sometimes but the alt never had to be replaced 180k miles before i traded it in

yes thats the security i'm referring to. little red blinking light just under the volume ****. How would i turn uit off? will it lock up soon as i unplug the stereo?

Question is, did you set the TheftLoc code? Or did the previous owner do it? If you don't know it, try this to remove it...

1. Press and hold presets 2 & 3 for about 10 seconds until the first 3 digits of the display code are displayed
2. Write the numbers down.
3. Press the AM FM button, write down the next 3 numbers
4. Call 1-800-537-5140, when asked, enter 202107, press the “button” and enter the 6 digit code from the radio, you will get an unlock code, write it down.
5. Go back to the car, press the HR button and set the first 2 numbers, then press minute button and set the next two last numbers, press AM FM button, SEC should be displayed, turn on radio
To remove customers code, repeat step 5. you should see --- on radio face, the code is now out of the radio