Leak behind shower base

[cookeville34]

Hi, I have a 1979 Soveriegn 31', I've got a couple of plumbing questions. 1)There is a leak in a pipe somewhere at the base of the shower, is there a trick or good way to get to this area? 2) How does the toilet work, it has a gas line going to it, we want to use water. 3) Does this trailer have black & gray tanks, when I had the water running it was running straight out a pipe under the rear bumper, doesn't look like there are storage tanks to me. Thank you.