Besides, I've fixed / expanded / rearranged my own electrical wiring more than once (which is legal here without a license, if you do it on own property for non-commercial purposes) and I didn't use any of my electronics knowledge. You just need to know what the wire colors mean, employ some basic safety procedures, and don't do stupid things with wire size and currents.

Well the first rule of electrical work is to assume an idiot or a cheapskate did the original work (or most recent repair) and the colors have a fifty-fifty chance of lying to you...