AC Commander is very similar, just the the field and brushes in the right place. If it runs backwards, swap the brushes. Other than that, it's just like installing the Cruise Commander.
FWIW, before I install any of the ERR boards, I open up all the terminal blocks. For the Cruise Commander with the larger terminals on the heatsink end, I unscrew the screws and use my dental pick to push the tab open to allow easy insertion of the wire.