I avoid buying anything from a dealer. They are not the most honest and they have overhead that private sellers do not have and therefore can sell something for less money. If a private party lists something at dealer price I would not bother. Bottom line-something is only worth what a person is willing to pay for it. If it is not selling then it is overpriced.
One thing to check...Go on the roof-there will be a rubber gasket that covers the connection from antennae to cable through roof. Lift it up and make sure it is not rusted. Last year I didn't get the same channels as the year before at the same site. Checked that connection and it was rusted. Replaced and made sure gasket was tight over new connection. No trouble since.
And I get way more channels than I ever did with better picture since the airwaves have gone digital. I did add the wingman.
"Cut out only the rusted material and glue in a piece of metal to repair the hole. Then just cover the entire outside AND inside with one layer of fiberglass cloth and resin. This should fix the problem and prevent it from happening again."
This one gets my vote-easy permanent solution!
a toilet bowl holds about a gallon of water. Any time I empty I refill with 5 gallons of water (5 toilet bowl fills) to prevent a poop pyramid from forming in the tank.
Regarding bleach- I would never put bleach in the black tank. Bleach will kill bacteria-bacteria is needed in order for the poo to break down. If you think you already have a poo pyramid then I would agree with the ice suggestion.
From the sounds of it-it may be a venting problem. Sometimes the bottom of the vent pipe sits too low in the tank and thus does not work properly making it smell in the rig.
So put in 5 gallons when emptied and then a liquid conditioner of your choice.