Bob,
I cannot comment on your specific throne and installation. We had a similar leak and decided to replace the inlet valve. After watching Youtube videos I ordered the parts for our Thetford throne so that I could replace the valve and seals.
It definitely is not the most pleasant task but quite doable. You can do only the valve if you have sufficient space and like working in very tight spaces. Complete removal was a lot easier for me. The culprit was the inlet valve that had a lot of micro cracks, probably due to freezing even when it was winterized. The removal and reinstall is pretty straight forward. The only issue was that I must have installed the one seal ring incorrectly and needed to redo it. My advice is to check the operation before reinstall of the throne, assuming you will be removing the throne.
The outcome? The throne works even better as the original had some operational issues from when we bought the coach.
Martin