its not hogwash. 123.00 covers the hour diag time. during this itme a tech should short test the vehicle to see if any faults are stored in the transmission and find out whats leaking. he should then check the fluid level to see how much has been lost. as far as the trans pan goes some of the ZF transmissions had aluminum pans that the gasket could not be replaced separately. the stealer also told you that even after the trans pan replacement you still could have a bad transmission due to the fact that it is slipping. If they replace the pan and the trans still slips, who eats the cost of whats already been done? exactly. also the dealer is just trying to cover all bases. they do not want to upset you by telling you it needs a trans pan only to find out 1000$ later that now it needs a trans. they wanted to lay it all out on the table for you and i agree with them.
the "case open" you spoke of is what they call PUMA. it is an advise line for dealerships that allow techs to talk directly to engineers and specialists.
I understand that this is all not good but i believe the dealership is doing all that they can and giving you all of the information available to them. any further questions i will try and answer them, hope this helps some.