Yes, it is boxed in, so the only way you can inspect the tank is by removing it. I would recommend filling it up with water, and looking for leaks. If you don't see water dripping, then you are probably OK. The connections to the tank are usually visible via a hole in the subfloor, usually under a gaucho or some cabinetry. The Water pump usually sits on the floor in the vicinity of this hole as well.
To remove the tank, you have to unbolt/rivet the piece of angle that forms the front of the box/frame underneath. This will expose the edge of a 1" thick piece of plywood that the tank sits on. You then need to pull this piece of plywood forward toward the tongue, which will allow the tank to drop down. It is a bear, as the plywood will have expanded and bonded with the rusty angle iron frame. Not recommended just for the sake of an inspection.