I did it once on my old terc. It's under the driver's side dash, I think (follow the sound). Remove the lower cover, 5 screws, reach in and unplug the connector from the buzzer. 10 min job tops.
In my 86, it's in the right side of the dash (passenger in the US), next to the speaker. Unplugging it wasn't that difficult, but I plugged it back in after I locked the keys in the car the second time.