I've done the draining of the torque converter, and it was
a tough, long, nasty job. The really ugly bit was getting
the plug on the TC to line up. That required turning over
the engine with a big ratchet on the harmonic balancer.
THAT required taking off the fan to get clearance. *THAT*
required pulling the fan shroud. Ugh.
If I were to have the opportunity again, with hindsight,
I would almost rather do two sequential drain-and-refill
jobs with just the pan plug. Cases of ATF are a lot less
expensive than my time by the hour.
Two changes in a row will still leave a certain fraction
of the fluid dirty. If the fluid were really in a terribly bad
way, I'd just go ahead and do the scut work to drain
the TC. But certainly would not enjoy it.