I moved into a house built in 1900, and it would seem that the electricity in a few rooms haven't been updated. The LR, attic & basement all have 2 prong plugs. My question is how extensive/hard is is to re-wired to 3 prongs? Right now I'm usinf adaptors to plug things in, but they aren't grounded. I'm getting a large tank soon (75 gal.) and I can't plug anything in because the wiring is too old. All of the other rooms in the house have been re-wired to 3 prong outlets. How hard is it to do? Does id definently require an electrician? How expensive am I looking at?