You have to replace the unit. It is not just the buzzer. It is a rectangular box about the size of a cigarrete pack. I do not have the part number, do an inquire with Fastlane or Partshop.
Obviously the instrument cluster has to come out. With the part in hand, there is no way you can miss it.
I do not see a way to change the tone of the buzzer. They are not too expensive (if I remember correctly). It was around $50-60.
Mine just quit one day. No problems with the new one.