I rebuilt my Traveler toilet last year and found it easier than expected. Start by downloading the manual:http://http://manuals.dometic.com/
You may need to buy parts from Scamp
(gaskets) or your local RV shop (gate valve) but I found most of the parts in my local hardware store.
As stated above, the wax ring may hold the tank tight to the floor. So first remove the water supply line, vent pipe (I had to cut this), toilet, and sewer pipe underneath. This also had to be cut so I could remove the threaded pipe from the holding tank.