Whilst your in there inspect brake shoe linings for wear and grease contamination, electric brake shoe wear and drum scoring. If your repacking bearings replace axle seals. Other critical function is to check is operation of the break away coupling, the age of the coupling battery and its condition of charge. I would also be lubricating the electric brake shoe lever pivot and the points of contact for the brake shoes on the backing plate. After reassembly check hand brake operation paying attention to condition of cable and the brakes releasing.
Reassembly should involve torqueing the wheel nuts to spec and correct tyre pressures.