RV Repair: Black and Gray Water tanks removal and replacement, jayco dealer, toilet flange

Question
We bought a used Jayco Class C 1985 Diesl  motorhome. We are gradually working on each system as it has problems. We have leaks in the black and gray water tanks and decided to replace them.  How is the tank fastened to the toilet? Also, how does the vent go into the tank? We have bought new tanks but don't want to break anything getting the old tanks off. We need a step by step direction, please. We have removed the screws on the flange and disconnected the sensors and the waste valve but cannot get the tank loose from the pipes. We can't see whats up there

Answer
I am not familar with how Jayco builds their coaches but normally, the toilet flange screws into the tank.  Once the flange is unbolted or unscrewed from the floor, you should be able to unscrew it.
The vent pipe might be glued in, screwed in or just a collar fit.
If you want step by step directions, please either contact the manufacturer or a Jayco dealer.