P0788 -error code on my 2008 chevy silverado

Question

How hard is it to find and replace the shift timing solenoid? I have a 2008 chevy silverado with 70K miles on it and this code has come up twice in the past two weeks. Check engine light went off a week ago, but it now back on and staying on.
Need to know where it is located so I can check for a short first.