irlandes, automatic transmissions in general do not tolerate clutch slippage very well. I agree with you that the damage has been done, and the transmission is on borrowed time, fresh fluid or not. I wonder if the 3+ quarts is all that drops out if you do a pan drop on this car?
Question regarding Flush:
What do you use for transmission Flush? Same ATF or some other fluid to flush then will it up with ATF? How much ATF cost (in general)?
Transmissions aren’t really “flushed”. What they do is use a fluid exchange procedure, in which they pump in new fluid, removing all the old stuff. It’s a terminology they use that isn’t accurate.
Without the specialized tools, you cannot do this yourself. You can drain and refill, though. Normally, that’s enough, if you keep up with it. Every so often (opinions vary), drop the pan, and change the filter.