One other item of concern; if it is the transmission and if it were my car I would replace the radiator along with the transmission repair. Reason? Because the radiator cooler portion of the radiator is known to become clogged with metal filings from the tranny. Those filings can re-contaminate a new transmission which can accelerate transmission failures. There are shops that have flushers which can flush out the cooler but why risk it? Radiators are cheap when compared to the price of a transmission repair. I have yet to hear of ANY transmission shop recommending the replacement of a radiator along with a transmission rebuild. You have to ask for it because they will not suggest it.

Also, I'd use synthetic transmission fluid which has a longer life and lowers the operating temperature of the transmission.