[sourdough]

About 9 years old. Owned 2 months with lots of issues. Not winterized last year and unknown history before that. For mtce. that is important.

I would replace the toilet as you said. Get the 310 or 320, whichever you prefer. Not knowing how you set the trailer up initially, turn off the water to the hwh, pull the plug and drain it (with the pressure lever open). When empty replace the drain plug and close the pressure valve. Turn on the water and let the tank fill. When filled (water quits running) open a faucet on hot and wait until water flows without sputtering and blowing. Hopefully the valve will not be leaking. If it is I would replace it and then see what happens.

I understand the reasons for replacing the tub and agree. I have never done that so can't guide you other than to mention that you need to be aware of drain/water inlet locations as you plan it - and realize that "remodeling" an RV bears no resemblance to working on a regular house. I've done several S&B bathrooms but not an RV.