Wilseya

My 2016 5.3 6 spd auto went into limp mode / engine power reduced. I get 4 codes P279A - Transfer case high range incorrect ratio. (I understand possible trans slip) P0446 Evap vent ( possible gas cap) P16f3. Transmission control module redundant memory performance. What do I need to do to fix this? P0777Clutch pressure control solenoid stuck on. How do I Locate this solenoid? Can I replace it without removing the transmission?. Thank you all in advance for any help. Ps o did buy a book Haynes Repair manual it is worthless to say the least.