Hi mcgiverson,
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.
If you have a round plug to unscrew just below the shower control that will be where you get to the fittings. If you do not have that then you may need to remove a panel behind the shower that may be in a pantry or closet. I don't know the floor plan of your unit, but some others will jump in soon with more info I'm sure.
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.
Jim M