The scope of your project and the questions you are asking seem to indicate that you should take this up with the electrical inspector in your code jurisdiction. Each circuit has requirements based on load and location and use. Electrical construction of other than just minor addons or change is something that should go through the permit process. You may be able to get the permit to do what you want without engaging an electrical contractor...the main thing is that the electrical inspector will make sure you are building something right, safely and in such a manner that your homeowner insurance will not be voided. If you can find a copy, the TimeLife Basic Electric book is my favorite for showing how to do electrical repairs for the novice. Luck, Kizmet