Hi Kaumahunter,
Welcome to the Heartland Owners Forum and to the family. We have a great bunch of folks here with lots of information and all willing to share their knowledge when needed.
I don't have a North Trail, but looking at the Heartland site pictures, I am guessing that it is under the sink/counter area. Look outside for vent and go to same distance from door, most likely you will need to remove a drawer to get to rear of water heater.
Be sure and check out our Heartland Owners Club. Join us at a rally when you can and meet lots of the great folks here and make friends for a lifetime.
Enjoy the forum and your new unit.
Jim M