Which MODEL???
Some the seal can be removed/replaced w/o having to disassemble toilet (can be done w/o removing toilet)
Some you have to disassemble toilet. (Easier to do by removing toilet)
WAX Ring....
RV toilets use a 'foam gasket' between toilet and floor flange
So WHAT MODEL?
Many times seal/ball just need a thorough cleaning/lube job
Turn water off
Open Ball and using your hands (you can wash them afterwards!) go over the seal flexing it/feeling it/removing any mineral/stuff on it.
Then put some dish soap in your hand and scrub seal top/sides/bottom
Do same with ball ....clean it across top surface
Then rinse seal/ball clean
After rinsing all soap off lube up seal & ball with plumbers grease (OR Olive Oil)....no vaseline ---it is sticking & can attract crud