Be careful if you have a shop that is not a trailer shop work on your
electric brakes. Brake cleaner sprayed into the magnets will melt the
insulation of the windings and wires.
As has been recommended on this list, it's best to replace the entire brake
assembly when the linings are worn out rather than just having the shoes
relined or replaced.
Drums can be turned but are best replaced if badly worn or scored. The
electric brake drums I have seen were quite thin, with no boss on the open
side to reduce bellmouthing.
Al Grayson