Hi Phil,
Yes, you can unplug it. Mine failed and the batteries inside it leaked and destroyed the circuit board. I actually removed it and drove the car for a year without the alarm / siren installed. I had no issues. My wife did buy me a new siren for Christmas. The new sirens have the chirping sound when you lock or unlock the doors. You need to remove the windshield wiper arms and plastic cowl. Easy to do but you may need a puller to remove the wiper arms. There is a procedure available on this forum. Look through the area where all of the procedures, troubleshooting help, and data information is located. Hope this info helps.