I have done Italy twice lately. My suggestion is rent a car.
It's a little scary in rome but when you start to drive like they do it becomes no different then driving in any big city.
Do not make eye contact with other traffic just go where you want to. they expect to have to use their brakes..
Once your out of Rome it is very easy to go anywhere else in the country.
Greece I know nothing about, but hope to soon.
Woody.