Hi,
I created a set of checklists for the GTN using the Garmin ACE.
They're based on the Just Flight PA-28 Arrow III manual and the Pilot's Operating Handbook from Piper. The file is attached to that post in the X-Plane.org forum.
If you spot a typo, error or anything else, feel free to fix it using the checklist editor (link in the aforementioned post) and share it.