Just rewiring should be easy and inexpensive. Wires are wires -- materials are cheap and anyone who understands how they work should be able to do it quickly. Just call up your local RV or trailer dealer and ask for a quote.
Usually brakes and lights run me a few hundred, including when the trailer guy found that one of our brakes on our new-to-us trailer had been put on upside down (??) and he had to change out a bunch of broken lights.
Call and ask - our repair guy is always pretty good at giving an estimate that is fairly accurate.
"Life has sent you this gift. God has sent you COTH to help you make the decision."
Actually, wires aren't simply wires. Cheap wire is just that-cheap wire. A lot of trailer wires for some time now has been copper coated steel, whether on a horse trailer, or a boat trailer. The copper coating gets comprimised for all sorts of reasons, and the steel rusts. Rusty steel is a poor conductor. Rusty wire on a rusty connection looses the ability to ground, and without a good ground, even the best connections everywhere else mean nothing.
Using crimp-on connectors just compounds the problems.