Hello and welcome.
Are you referring to a transmission related solenoid, or a shifter related solenoid?
This sounds like one of the transmission shift solenoids.
These solenoids are located in the valve body of the trans.
The side cover needs to be removed.
Quite a big job.
The engine / trans assembly, along with the frame needs to be lowered on the driver side to remove the cover and get to the solenoids.
Not even something i would attempt in my own garage.
Yes, that is correct.