freezer froze and warm

Hey everyone
My ge french door fridge is acting up. came home from work today to find out my freezer wasn’t as cold as it normally is and in turn the fresh food part is warmer also.
took the shelves and back panel out of the freezer and viola coils are iced up solid.
I know there’s at least a defrost timer, thermostat, and heater but don’t know where to start.
what should I check first?
I’m not for sure where the defrost timer is. i think I found the stat and heater though.

thanks for your time

libi