If the fluid is low, filling it back up may cure your problem. Well, except the problem of where did your fluid go to cause it to be low.
More than likely, if the fluid is full, whatever damage that has been done isn't going to change by changing the fluid or adjusting any bands (which I don't recall these having adjustable ones). Dropping the pan will give you a lot of insight as to what may be going on (lots of material and junk laying in the pan) which means no amount of clean fluid is going to help.
There is also an outside chance you have something else going on (its an electronic dependent transmission) meaning there could be a sensor somewhere, even on the engine, giving faulty readings to the system. A trip to a competent repair shop may not be a bad thing, but for a diagnosis...not just a fluid change.
I'd be leary that AAMCO will want to sell you a transmission. They still have boat payments to make in winter!