Northshore,
We have the same Lance 165-s-ex cab camper; maybe not the same year but close. We have found over time:
1. Pull the shower curtain completely around into a "U" shape with the vent and door open. Be sure the drain stopper is open.
2. Have a couple extra shower curtain hooks to snug up the ends (to stretch out the shrivel) to the shower wall. This is where the water has the best chance at intrusion. There are small stanchions for that purpose.
3. For anyone 6 feet or taller, sit on the pot and use the wand in short spurts. I always sit to sxxx, shave, and shower. To shave, I usually put my left knee on the lid down pot with my right foot in the aisle to get up close and personal.
4. After you have regulated the temperature, use the rotary on-off dial on the wand to conserve water, ala "G.I. shower", continually hanging the wand back up. It is made to leak a little. I always open the lower sliding door to dry after the curtain is back behind the commode.
5. We have never seen any water intrusion anywhere in the shower room that did not dry up quickly in our desert southwest climate. No dry rot. No discoloration. No mold.
6. If you have qualms about water repellency, use a caulking gun with clear, high quality, non-silacone RV caulk to seal the edges that have the most exposure. You may need actual technique for this. It looks worse than it really turns out to be. Again, we've had no problems with water in the bathroom area during the 15 years/230 nights we've used the Lance.
If you live in the desert southwest, and "can't get no satisfaction" with the above, try as we did by purchasing a stand alone pop up outside shower enclosure and use the external shower wand. It has worked out very well in the boonies. Not so well in organized campgrounds.
So, in short, it's not worth putting all that time and money into an old relic. How would i know? I keep trying.
jefe