Hello I will help you with your question,
This is quite an involved process that you have to take the valve body out of the side cover of the transmission.
The procedure is below, look it over and let me know what questions you have
click here for procedure
Would this be very expensive for a transmission mechanic to do?
The "book" calls for 2.6 hours so expect 4 hours labor and $250 in parts, they may find the harness rubbed through which would cut the parts cost. So if the solenoids are replaced it would be about $650.
Let em know how I can help you with this