Really its an easy fix and Timoyz is on the right track especially about the system operating off of resistance. Yes its gonna be expensive, especially if you replace all of the wiring from the monitor to the tanks. However you can do it the way Im going to explain and should lose little to no continuity. Like Timoyz said. solder the connections together, this is how we repair wire bundles that get damaged on our aircraft (full size ones not RC). So while your out getting your wire to make your splices you need to get some heat shrink tubing. Cut your heat shrink about a half of an inch longer than each side of your splice. Slip the heat shrink on BEFORE you solder your connections together. Once youve gotten your splice soldered up. Slide the heat shrink over the soldered connection and heat with a lighter till its a tight fit over your solder joint. I prefer to use the heat shrink over black electrical tape as its weather proof. Where the electrical tape will fail over time.
The cost I was expecting from the RV guy anyways so...that won't be a killer. The way you're describing sounds exactly how my friend and I had discussed doing it less the shrink tubing...good idea to use it. Thanks for the advise..