Ford called and said my buddies 4x4 shift solenoid went out. They are gonna order the part for $30 plus some kind of valve. Im gonna install it myself where exactly is it at? IS it hard to install?

 

Guys this is my truck. As I stated in some post last week about my 4x4. They ran a diagnostic check and said it was my 4x4 shift solenoid and a valve body. Total was about $48. Where is this solenoid located? IS this a easy fix?
Thanks