Hi turkey,
Over the past 4 years I think I've read posts from maybe 2 or 3 brave souls who dropped one of their tanks for one reason or another. Most of the time, this level of repair is left to a dealer service tech. I don't know if anyone has done this on a model/floorplan like yours, which might be another reason no one's providing the guidance you're looking for.
Realist has a point. If you drop the coroplast, you should be able to see the bottoms of the gray tanks and the supports holding them in place. I'm afraid I can't shed any light on how the drain and vent pipes are attached. Maybe when you let the tank down they just slip out - but I don't know.
Leaks are tricky. I had a leak from gray #1 that I looked for repeatedly. Turned out the tank heating pad had burned a couple of holes in the tank and because it was intermittent and hidden by the heating pad, it was pretty hard to find.
A leak on top of the tank could be from a cracked drain pipe. On my gray #1 tank, I could see from inside the basement (with the wall down), where the pipe was attached. Maybe you can on yours. Some exploration required.