Just changed the toilet in mine and had to change the orientation of the flange so the toilet bolts were in the right position.
The flange is screwed into the floor with four big wood screws. There was some silicone/RTV on the pipe portion of the flange where it nested into the pipe going into the tank -- just twisted the flange until the film of sealant/adhesive broke free, then cleaned the surfaces and re-applied fresh sealant and made sure to twist the flange assembly 360 degrees back and forth to spread a new film of sealant, then screwed it back down in the correct position.
The toilet seal on mine (Thetford) is a soft closed-cell foam material. Probably used because it is compliant and springs back in a motorhome that's subject to vibration and temperature extremes -- a residential style wax ring wouldn't do as well.
Eric & Holly + 2 kitties from New Hampshire
1992 Winnebago Adventurer 32'