I hate wiring

So I bought new headlights at $25 each and installed them. Turns out I also had to replace the dimmer switch which cost me $6. But the headlights work great now! On to the tail lights. Not so good. Brake lights work, turn signals work, but the back up lights don't. So I use my Haynes and Chilton manuals to troubleshoot the problem. Nothing listed. SOB. My father and I started tracing the wiring and have found that the wire is cracked in several places leaving exposed wire as well as several breaks in it as well. So what does this mean... I have to replace the wire. Well part of it hopefully. Simple sounding enough but a pain in the ass because I have to trace it starting with the switch on the transmission. But I might as well check that while I'm there right. So i'm slowly working my way towards passing the inspection so I can drive it legally on the road. It will get there.