Hokay, all done at Discount Tire.
It took about an hour to replace all five tires. Five new metal valve stems, 24 new one piece lug nuts, install, warranty, and five date code 1610 Michelin P235/75-15 108xl tires. They ran them to 50 psi. I'll check torque to 110 lbs as we go.
All well headed back to the RV Park, coach felt similar but maybe slightly firmer/steadier? No issues at any rate.
I'll be reprogramming my TST507 sensors for the new set pressure (still +\- 20% though, right?) but I will leave the alarm temp at default (I think it is 158F?).
Just wanted to say 'thanks' to everyone who took time to comment in the thread, and particularly those who PM'd me with help. I deeply appreciate it.