P1779 FORD - Transmission Light

Question

The Transaxle light on my 2003 Ford Taurus Duratec has been coming on intermittently. Never in the morning, usually only in the afternoon when its hot out. I had the code read at autozone P1779 and a mechanic told me I need a transmission overhaul for $2500. The car runs perfect, transmission shifts perfect no mechanical issues. Can this single light coming on cost almost what I paid for the car?

Thanks!
-Drew