The switch is mounted on top of the transmission housing, to the
driver's side of the engine, and can be seen by looking down just
behind and below the battery. It is easily removable using an 7/8"
deep-set socket and extender. The part is available at auto parts
stores as well as Saturn and should cost $16-17.

You can see some pictures at
http://home.comcast.net/~williamkilg...up_switch.html