BE SURE AND DRAIN THE TANK BEFORE YOU START THIS. Otherwise you will get very wet.
On the '04 journey. To replace the seals you need take an access panel off on the front of the metal enclosure that surrounds the fresh water tank. The valve is behind that panel. I drilled a couple of holes to put a socket thru to disassemble the valve. You need to take the seals to a camping supply to make sure you get the correct replacements. The valve on mine is a 1.5 inch. There are 2 different seals for this valve. I put vegetable oil on the new ones before installing them. Put the replacement seals on the outer flanges and then put on valve body. Hopefully that will stop the leak.
I have attached a couple of drawings. One from Winnebago and one from the valve mfg, Valterra. They will give you a perspective of what things look like.
Hope this helps.