1. Depends upon the original kit size. 5 gallons may or may not be enough. I'd get 6 to be sure, it won't go bad.
2. You are going to be tight with a 6.5 gallon fermentor. 6 gallons of must plus the skins will come out to just under 6.5 gallons. IIRC a standard fermentor bucket is 7 gallons...