Try a different title that gives more info.. like Help.. rewire needed, but where to start?
Have you got any boat yards around you? try them to start with and get a few costs etc... Another angle might be to see if anyone can help you do it... for the cost of a few beers!
I am not an electrician but have extensively reworked the electrics on a 32' river cruiser and am now about to do same on a Princess 32. A 21 foot boat shouldnt be too difficult to do yourself with a little advice or I could assist for a reasonable fee. I am only about an hour away from the Medway
Contact me via private message if you are interested.