[fiberglasscivic]

The safest way to ensure that your buyer can use it is to call a local chevy dealer and have them give you the anti theft lock code. They will need the serial number. I don't know if they will need proof of ownership or not. My local acura dealer didn't.

You won't need the special wiring harness. The reason someone warned you about it was because chevy has some stereos that use an external amplifier. From what I understand, none of the 97-02 malibus use a system with an external amplifier. Even if you have an external amplifier then you are going to need a basic wiring harness. For the amplified systems there is a line level converter that goes inline between the adapter for the car and the plug for the stereo. I've installed an aftermarket stereo on an amplified system without the line level converter and didn't have any problems. Either way it goes you should be fine.