Changed the Seal!
Update: Thetford Aqua Magic II China Toilet (side pedal) wasn't holding water so I changed the seal. Turned out the fix is not that big of deal. Just followed the step-by-step instructions that came with the new seal. They also give you a new one for the drain connection instead of a wax ring. In cost me $11. From start to finish it took 20 minutes. The toughest part was getting the screws in the floor flange back into the holes in the base of the toilet as they float around. Needed a helper to line up the screws as I was lowering the toilet to the floor. Toilet now works good as new!