With help from my friend Viktar, solenoid control panel was installed, wired in, and tested.
Side cover installed
Side cover panel
Head ceiling light done
Fridge arrived
New head sink light
New outlet / head
Ambient light in the cabin
First toilet flush test
Well, after all the hoses and wires were connected the toilet appeared to be dead. As I started troubleshooting, I realized that an inline fuse holder was wired into the +12V wire from the battery but I never actually put a fuse in it! Once that was fixed, we were in business. No leaks, no troubles. Happy!