Well, I'am going to be the voice of decent and state flatly that there is nothing wrong with the Nissan wiring design. Many of the electrical components reflex the level of quality consistant with the Japanese car industry of the 1970's. Which was mostly a mixed bag of: not bad, so so, and not so good. When all the conponents work properly the design is flawless. I find no extra or worthless wires.
Most of the problems the poor car gets blamed for are caused by the string of boneheads over the last 30 years that have tried to "custom" install audio systems, extra map lights, and other gizmo widgets. I've seen failed switches bypassed (wrongly) and replaced with cheap Radio Shack crap.
So, what are you going to do with the car? If this is going to be a stripped out race car then yes, pull out the stock wiring harness and replace it with an abbreviated one. You can probably make it yourself for less tham $100 with good quality parts.
If this is a street car that you want everything to work just like it did when it was new than fix the problems, replace the failed parts, and follow the JTR book to wire in the new V8. Don't be intimidated just because you can't fix it with a wrench. Auto electrical is not rocket surgery. Like Tim says, buy a little book and read up. After an hour reading your anxiety about wires will fade away. Buy a $10 digital multimeter and start having fun.
And the bonus. The next time you or a friend have an electrical problem in a car you can fix it! You'll be like Superman!