Hi Gill-7767,
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 suggest you drop the bottom cover on the side where the sewer hooks up. You should be able to see the sides of your tanks and maybe even get to the valves without cutting the plastic cover.
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 to you unit.
Jim M