Re: overwhelmed w/ electrical
One giant piece of advice: BUTT SPLICES ARE THE DEVIL. A butt splice is a crimp on connector that looks like a tube. You stick one wire in one end, crimp it, then stick another wire in the other end and crimp it. DO NOT USE THESE. EVER. If you ever want to contemplate suicide, then spend some time troubleshooting an electrical system with intermittent failures, i.e. bad connections. It is darn near impossible. Butt splices are a guaranteed point of failure and source of endless headache. Butt splices exist to get you out of a jam, like a band aid. They are the mark of incompetence in any other application. The fact that you see them everywhere doesn't change that.
In the event that you have to extend a wire because you cannot replace it, use two crimp on ring terminals with a #6 bolt/lockwasher/nut and then use vulcanizing tape to seal the connection. I would never suggest to extend a wire instead of replacing the run, but in 20 years of marine and factory electrical work, there are times when it must be done.
If you have to relocate a panel: rather than extending the wires one by one, put terminal strips in the existing location and use it as a junction box. Properly labeled and landed terminals will aid greatly in future troubleshooting. I'm a huge fan of cage-clamp terminals, but most people prefer screw terminals because they aren't familar with the cage clamp style. Part of this is because cage clamp blocks are expensive.
Don't skimp on wire. In the big scheme of things, the wire is the cheapest part of all of this and the hardest to deal with once it's in. If you have to cheap out somewhere, don't do it on wire. Plan to waste several feet of every run. YOU DO NOT want to run a wire through bulkheads, under the sole, behind the cabinets,etc only to discover that you are a foot short when you go to land the wire. Leave a loop of wire on long runs. Years down the road you may have to cut a corroded connection back. It sure does help to have a few extra inches of wire that can be pulled when needed. Your runs should not be banjo tight. Your boat flexes and your wire should never be under strain.
Save your cut scraps and use them in your switch panel, etc. It's great to be frugal, but cheaping out or under-buying is false economy. If you don't have time or money to do it right, you certainly don't have the time and money to do it twice.
I'm not just a blowhard, although I may be that. My background: I began my career as a Navy Electrician. I then went on to a career in automation, controls and robotics, marine as well as manufacturing. In twenty years I have been guilty of doing all the stupid things I list above and I learned the hard way to avoid doing them again. Do the hard work up front so you can enjoy your boat down the road. Nobody wants a nightmare that just won't end, and nothing turns into that more than poor electrical systems.