If you want to fix that wiring without spending an arm and a leg, here's a tip for ya. Often times it's just the exposed portion of the harness that's rotted. Everything under the electrical tape (all 500 feet of it) is usually quite soft and....supple....yeah.....oh yeah, so what I did just cut off and solder on new sections of wire a few inches past where the electrical tape ends.
While your at it you can put new rubber grommets on all the connections or update connectors to anything radioshack has. Gets lots of shrink tubing too. Personally I removed all 500 feet of old brittle electrical tape from mine. Even in the dry desert that tape did it's job and kept the harness in very nice shape. It's a little time consuming but only costs around $150 to do everything, which beats $1000+ for a whole new harness. After I finished with everything I rewraped all 5 main harness's in new electrical tape. Where the tape stops, I like to make a little electrical tape bow tie which keeps it from ever unraveling as the years go by.
