Just found this great 6-Part series that clearly explains a lot about the practicalities of driving a car in Italy for foreigners. I found it really helpful - have not seen anything better really.

Part 1 - Overview

Part 2 - You and the Autostrada

Part 3 - Understanding the Signage on the Autostrada

Part 4 - Autostrada Rest Areas

Part 5 - Paying Tolls on the Autostrada

Part 6 - Buying Gas for Your Car