May just be the "conductor plate" in the transmission, if so, then about $125 for the part and another $70 for a filter and new fluid.
This can be done by any competent DIY mechanic.
( Could also be the TCM ( Transmission Control Module ) located at the front of the passenger footwell, a new one of these will cost around $100 and up depending on the source. The TCM is a plug and play replacement.

Last thought : maybe all the fluid leaked out ? This would be the transmission connector, about $15.