Tanks on 5th wheel, how many and how do they work?

Based on your description of the panel, it has 2 gray tanks 1 for the kitchen sink (galley) and the other for the bathroom.

And I’m sorry to hear of your loss. I know what you’re feeling losing your spouse.
I pray things get better for you.
Replacing or repairing the valves is not terribly difficult for anyone with basic skills. But might be a schitty job… Even a mediocre repair man, if honest, should be able to get it done for ya.