I believe that behind the panel, the wires connecting the G1000 to the 3 or so computer boxes can be removed one-by-one, rendering each instrument on the glass face inoperative. - However, this should never be done without a technician.
Another option is to black out or cover the screen entirely. This one I've seen done before by pulling the circuit breaker to the monitor for an example on the ground, not in flight. Do note that this kills the display entirely, and is not recommended to be done without a technician, if at all.
As required by Transport Canada or C- registered aircraft, the aeroplane must be equipped with a traditional ASI, ALT, and HI underneath or to the side of the G1000 in case of an electrical failure, as well as a traditional magnetic compass that is usually mounted on the dash. If that is followed, the previous might be able to be done. However I've never attempted it, and I probably never will - Again something that should be approved by a mechanic/technician.
Under normal training, I've never had the attitude or heading indicators blocked out on the G1000. Sticky notes are used to block out instruments on the second 172 that does not have a G1000 at my local flight school.
As a last (and most realistic) option, refer to pages 6 and 8 of this manual on the FAA site: https://www.faa.gov/training_testing/training/fits/guidance/media/g1000.pdf
Hope that answers your query