Correct, the backup light switch is part of the transmission range sensor on the left side of the trans. In fact, the adjustment procedue for the sensor is based on turing it until the back-up lights come one, or something like that.
If you are going to change it, take the opportunity to replace the shaft seal as well. It looks just like a mini-wheel seal, and it only costs a few bucks.
Autozone has them, for about $50. They list it as a nuetral safety switch, although it is really a transmission range sensor.