Wow - the vote is 2 to leave alone - sound easy enough :-)
The elbow joints the plumber put in appear to be soldered well. It is
just the threaded joint where the stop valve was installed. Luckily,
the seepage is on the exiting side of the valve so if the leak should
ever worsen, the water detector will automatically shut the water off
to the heater.
Interestingly, there were hard mineral deposits on the hot water exit
pipe joint on the copper flex-tube. There must have been a seepage
when the older water heater was installed and it sealed itself with the
mineral deposits. The seepage returned there last night as well but
after a few hours, it was bone dry. I am hoping that the same occurs
with the joint that is currently seeping.