Step 1: Unscrew all 6 tiny screws across the bottom of the sensor bar. They turned out to be in there really good, so I had to use a pair of pliers to get some additional torque.
Step 2: Carefully separate the bottom piece of plastic from the rest of the bar. It lifts off really easily, no sneaky glue/hook surprises.
Step 3: Take note of the wire colours here. If you forget, there's a 50/50 chance you'll mess up!
Step 4: Cut the sensor bar wire after all the chewing is done. Strip it back carefully with a razor. Thankfully the wire is ridiculously long so there's plenty left over (good luck if it got chewed off near the plug!)
Step 5: Just de-solder the old wire and re-solder this newly stripped end. Make sure you solder to the correct pads on the sensor bar circuit. Then put it all back together and plug it in!
Conclusion: This is really, really easy to do and shouldn't scare anyone who's tinkered with electronics. Also it seems as though the Wii sensor bar is literally just a bunch of Infra-Red LEDs. No communications at all.