Fairly easy fix. Just changed my base to flange and the bowl to base gaskets out last month on my 2000 HR Endeavor. I was having odor issues and found both seals were leaking. New flange seal is about 1/2 inch thick and the old one was about as flat as a quarter. Mine had the carpet on the base and you could tell it had also leaked blue water at some time.
You just need to disconnect the water supply line, remove the trim from around the base of the toilet, if you have the foot flush you will need remove the trim from it as well, then remove the 4 nuts holding the toilet down. You should now be ready to lift up and remove the toilet.
The gasket will either be on the toilet or stuck to the flange. My gasket came with 4 new bolts and nuts, also easy to replace. Clean everything up, align the new gasket and re-install.
The gasket shown in the other post goes between the base and the toilet bowl. Mine was leaking there as well so I replaced both. For that one you will need to remove the large hose clamp that holds the base and bowl together. All of this is also easy to do if you remove the toilet from the motorhome, remove the lid and turn it upside down.
You will also need some rubber gloves.......
While mine was out, I ripped out the carpet, built a new base and went back with ceramic tile. Hated that carpet around the toilet.
Good luck and send me message if you have any questions.
Michael