Check the Forum section about toilets, they are fairly simple. Mine is a Majic IV and has a cover on the front that pops off revealing two bolts, one on each side. Once those bolts are removed and the water line is disconnected the toilet should just lift off the mount. Check other forum for inspecting and replacing the seal, I'm using a household wax seal in mine because of the flooring thickness that I have so it's not stock.
If you are thinking of replacing valves, keep an eye on the other thread that is at the top of the list right now "leaking grey water flush valve" by pal07, there is member who put pics of the plumbing when his was done. He did a conversion from the Thetford which we have, to Valterra commonly available and inexpensive but very good products. For example, 1 Thetford valve is around $60 but a Valterra valve is around $15 so you could replace the whole plumbing for a way less than one valve and when you need replacements it's a way cheaper.
For me right now, I'm need a short term fix so I can go to the beach in a couple weeks. I might buy a Valterra T58 (Thetford to Valterra converter) and a Valterra T50 (twist on valve). See this video
1991 34' excella 1000, bought 05/10, oak floors, granite countertops, Marble bathroom counter and floor, 2 A/C's, 2005 Hensley.
Tow With: 2006 Dodge 2500 Quad Longbox 2WD, 5.9 Cummins, Edge Insight CTS, Smarty Jr programmer, Bilstein Shocks, Ingalls balljoints.