I need some expert help before I do anything. So I have inherited this truck from someone who I can no longer get a hold of. I didn’t buy it, i was asked if I wanted and I said of course knowing there will be some surprises. The truck has been parked for who knows how long so I got a new key made and charged up the battery and once I got in and started the engine there it was the surprise of all surprises. Check engine light, parking brake and brake lights are all on. I let it run for awhile then put a scan reader on it and got this codes

P0730 Incorrect gear ratio
P0735 Gear 5 incorrect ratio
P0736 Reverse incorrect ratio
P0741 Torque converter clutch solenoid- circuit performance or stuck off
P0783 3-4 shift
U0155 communication with instrument cluster control module

The truck shifts gears and moves in Reverse but when in Drive, it doesn’t move at all. I forgot to mention also that I discovered 6 qts of Pentosin trans fluid with transmission filter kit. My question to you experts is should I start with having the trans serviced and check the valve body components before considering a replacement??