Brian,
I think that the leveling system reservoir on your Contessa is in the same location as the 2000 Patriot. If so, it is in the right side of the engine bay and just behind the basement compartments in the right rear of the coach. You access it from under the coach.
The hydraulic tank in the bay with your filters is for the engine driven hydraulic pump that powers the power steering and the side radiator fan.
Also, the kitchen slide and the hydraulic leveling jacks use the same pump and reservoir.
Gerald