I will be in Paris for 3 days post transatlantic flt. I WILL have extra luggage as I am renting a car and driving to Italy and staying 4-5 months helping a friend with a restoration. Is a shuttle the only option as I understand there is no luggage storage @ CDG?
There are, in fact, a luggage storage check-in rooms at the airport. At T2A it's on the departures level and at T2F on the arrivals level. I pretty sure there's one over at T1 somewhere as well. I've never used it and don't know the cost, but it's there.
Are you planning to return to CDG to pick up a rental car? Even so, if you're going to be in Paris for three days, why not keep your extra luggage with you at your hotel? That way you won't need to pay to store it. France and Italy are Schengen countries. Are you aware of the Schengen Rule? You cannot stay in Schengen countries more that 90 days in any 180-day period.
If you are planning on working there a Schengen visa won't help. You will need a working visa, you need to apply far in advance for it, and you can't get it there. Visa all arranged?
Depending on where you wish to go, the Roissybus is a cheap way into town, as is the Air France bus. See: http://www.parisescapes.com/paris_cdg_to_paris_bus.html