Bought the thermocouple. Installed it.
After two pages of how to get the damned thing apart and so on, thread in the new thermocouple, and start putting it back together, I get to this part:
"Reinstall the manifold tube, pilot tube, and thermocouple into the thermostat/valve.
[turn page]
IMPORTANT: Do not overtighten thermocouple! Use fingers to tighten nut and tighten only 1/4 turn with wrench!"
Too late to go out and get another one. So still no hot water. Maybe tomorrow.