Re: re wiring
I rewired my 29ft myself, started at the power(stern) and worked forward. I found much of the wire was still reusable, just added new ends. Make sure you have lots of connectors and ends before you start. Also a good wire stripper/crimper, and afew roles of electrical tape(will become your best friend). I only bought 200ft of additional wire and was able to rewire my entire boat.
Took me 3 days. Its not hard work, and i wasnt going full blast. I actually find it rewarding, stringing all the wires and then having things work when its done.
The trick is to get from point A- B in the shortest amount of space, but without the wire showing. When i pulled out all my old wire i made sure to leave 1 or 2 going through each tunnel or pipe, that way i could pull more through. As long as you make sure to never have no wires going through a certain point you can almost always get more through relativly easily.
12 volts isnt deadly, it will just keep you awake
Also the service manual for your engine should tell you how to wire up the guages. What sort of engine do you have? I have mercs and wiring the engines was the easiest part, just added extentions to the cannon plug, labeled which wire was what number, then strung them to the bridge, and played connect the dots using the service manual as a guide.