This sounds like a head scratcher and a whole entire can of worms.
You need a soldering iron already....do you have a digital multimeter?
I do not think you will be able to properly diagnose this without some electronic verification tests.
All of the tests laid out here take into account the car is running correctly. The damaged wires may indeed be cut out and resoldered but as long as the effected wires do not appear to have parasitic green corrosion. You may be able to get away with some contact cleaner, a small wire brush and some luck.
Here is the circuit in question-
There is the right way to do things and when I am being paid to fix someone else's car they get that without question, but when it comes to my car I am guilty of taking the easy way on a few things. I wrote an article a while back about relocating the knock sensor and making a new harness for my own car, I am all about saving time and energy when it is your personal car. Let's try to get this.
