Deb, I've driven all over Italy, and it's as easy as can be. If you've driven in other European countries, the autostrada is no different. Keep right except to speed insanely, and if you see a giant Mercedes or Audi coming up behind you fast, move over - at your convenience, no need to panic.
The autostrada are every bit as modern as American interstates, and in my opinion the driving in general is more competent and sane, with the caveat that some people do speed at levels above what we would consider reasonable.
I'd avoid driving into the larger cities until you're comfortable on the highways. And be aware that a lot of smaller cities have such narrow ancient streets that it's customary to park outside the city centre and walk in with everybody else.

But I've driven all over Tuscany, Umbria, Piemonte, Lombardia, Veneto, Friuli-Venezia Giulia, Trento, Emilia-Romagna and more (and also in Slovenia and Croatia, France, Spain, Germany, Austria, England, Ireland, yada yada, and I can comfortably advise that it's really not a big deal. Give yourself a day outside the big cities to get used to the local customs, the differences in signs and road markings and such, and you'll do fine. Don't worry about traffic circles either. Once you get used to the flow you'll realize that they make a heck of a lot more sense than stop lights.
