Not sure if one is available for the G1000, but Garmin has free downloadable simulators for their associated units. These have been very helpful to my students by doing ground with just the sim software so they can focus on just learning the box without the pressure of flying the airplane or the associated cost of running the aircraft.

When they do instrument x-c's on them I have fly it/program it on their own on the sim first so that way they are much better when we fly it.