Follow up....
The $5 flange seal (toilet to floor) did the trick. I really had to compress the new one to get the toilet flush with the floor and that should seal it for some time. The service guy suggested simple vaseline to help seat and seal the new o ring. I had trepidations about a petroleum product reacting with the seal, but he was adamant about it. Will see.
Two side notes,
The screw in seal (used it in the house when removing toilets) worked fantastic in keeping the smell out of the camper while the toilet was removed.
Thought of getting one of those water sprayers (termed water saver by thetford)while I was behind the toilet but was reminded by the DW that we have a 6 y/o son and how much water would end up all over the bathroom once he figured out how to use it. Nuff said.