The trailer that I bought, has electric brakes and electric lights.

The lights worked intermittently, such as worked only once or twice.

The electric plug is a two piece job, with wires held by screws, some
wires fell out. Not good enough.

I bought a replacement molded one piece plug with 8 foot tail, and
will use it. What I want is to do a good job rewiring the trailer. I
believe that the trailer body is used as negative ground, which is not
so great when there is corrosion. So I want to be sure that I follow
"best practices" and to know what they are.

Any suggestions?

i