This is the text missing from the Sierra Pro Pilot readme file for patch 1.02 Beta:

The new C172R. 
This plane does not have a carb heat knob. 
It has an EGT gauge.  
It has a GPS controller on the panel. This allows you to use the Nav1
instrument to fly  flight plan waypoints through the GPS.  Since the
autopilot also tracks the Nav1 instrument this allows you to use the
autopilot to fly to these waypoints. The important thing to remember is
that this only works when you are flying under a flight plan.  The
waypoint that is displayed on the GPS (when the GPS is in NAV mode and
the GPS controller is in GPS mode) is the waypoint that the Nav1
instrument will track.  The pilot will need to set the OBI on the NAV1
instrument to the bearing displayed on the GPS ( or simply spin it
around until the CDI centers with a "to" flag showing ), then if the
autopilot is in NAV mode it will fly to the waypoint.  Once at the
waypoint the GPS controller will begin to flash a WPT message meaning
you have arrived at the waypoint. The GPS will automatically switch to
the next waypoint and the pilot will need to adjust the Nav1 OBI for the
new heading. To use the Nav1 instrument, with the Nav1 radio, set the
GPS controller to NAV mode.

  The important points revisited:
     a. The GPS controller on the instrument panel determines whether
the Nav1 instrument is tracking the GPS or the Nav1 radio.
     b. The Nav1 instrument can only track a GPS waypoint in NAV mode
when flying under a flight plan.
     c. The pilot will need to set the OBI on the Nav1 instrument when
using it to fly to GPS waypoints.  This models the OBS mode of the GPS
model available on the C172R.

Brian Gallardo