Is the fried wiring external inside the trailer somewhere or around the water heater itself.
Usually a shorted out element will mess with the internal wiring of the water heater.
Being external wiring being fried would be a real pain to replace as all the wires are behind panels and under the floor possible etc... Not so much a pain to replace the wiring just getting to the wiring is the problems. Could be very time consuming.
If it is all internal water heater tank wiring it might be best to just replace the water heater for new one. I'd at least price one out and what the difference might verses the repair cost.