How do you disconnect the factory security on a 1993 buick park ave?

You cannot disconnect it but you can bypass it.

First you need to know the resitance of the chip in your key, then you can go to an electronics store and but whatever combination of resistors you need to match (or comver very close) to the value of the key. ( you can find exact values online if you search) Once you have those crawl into the drivers footwell and you'll see either two wires coming down the steering wheel or one thicker white one which contains the two individual wires (usually orange). Cut this. You can let the end that goes up to the lock just be, ther no electricity going to or from it. The wires going down will need to have the resistor(s) you bought soldered across them. Ive seen wire wrapping work but I've also seen them come loose.

Now you cars security system thinks it always has the key in it.

This is what installers have to do to install a remote starter by the way.