First, you need to know what the code(s) actually is.......
Most transmission codes that are set, will cause the PCM to command FULL LINE PRESSURE, which causes harsh shifts....
That's a lot of money for two solenoids.....
Yes you have to separate the ball joint, drop the cradle, and lower the engine/tranny on the driver's side, and remove the axle, to get the side cover off......if the correct procedure is to replace just the two solenoids, which I doubt if the transmission is shifting ok, what is their labor rate, and how many hours are they quoting, and are they doing a fluid/filter replacement also?
Also, is their work guaranteed?