Yes, your solenoid bank is barely accessible from L/S engine compartment. There is a cover usually retained by two 1/4" hex screws or thumb screws. This same style trans was used up until the D series wheel loaders.
Once you get the cover off, there is usually a legend inside that lists which solenoids are energized in which gear. Most often, in my experience, the wiring insulation crumbles, you'll have to be very careful or you'll be building yourself a harness.
The ECU is in the door that houses fuses and relays by your right knee
I can't confirm, but I believe we can use troubleshooting and service info for B-D series loaders.