Water valve leaks is common on some Thetford toilets. Easy to fix after you get the toilet out.
I would remove it then decide whether a new valve is worth it or not. We had ours leak a couple times, replaced the valve, but the main slider valve mechanism was getting rusty. decided just to replace the whole thing.
I replaced by Thetford Galaxy with a Thetford Bravura.
Bud
USAF Retired
Pace Arrow
2003 Chev Ice Road Tracker