I have a 1997 Lance squire lite 165s, same gray tank, same outlet nipple, mine looks exactly like yours and mine leaked also.
I went to Harbor freight and bought a plastic welder, I used the welder to fix the cracks in the outlet nipple, I could not find any filler rod that was compatible with the material of the outlet nipple (drainage part of the tank) I used the welder to fill in the cracks, I then used JB water weld (its a two part putty) and coated the entire drainage pipe. I did the repair with the tank in place, I figured I would give it a shot before removing the tank.
So far so good, no leaks.
I am wondering if in your model Lance the shower drains to the black tank, like mine did.