Don’t go to AAMCO or any other Chain, such as Cottman, etc. An independent transmission shop is your best bet.
Also, see Tester’s note on a possible Technical Service Bulletin (TSB) on this transmission. A knowledgeable shop might be able to make a repair.
Agree with you that a Flush is not a good idea, but draining the fluid and changing the filter is what should be done every 30,000 to 40,000 miles.