First of all, sorry about your transmission. But it happens, sometimes the Mechatronic brains of the tranny fails, sometimes it doesn't. It's just a ZF 6HP transmission that is also used in Audis to Rolls Royces. I guess they are crap too?
https://en.wikipedia.org/wiki/ZF_6HP_transmission
Secondly, when you have a car that is that old and worth next to nothing, why take it to a dealer? Find a good independent. They may also have options for refurb trannies.