Concerning the taxi ride from the airport. After you exit customs, there will be a lot of "taxi drivers" in the arrivals area offering to take you into Rome at really cheap prices. They are unlicensed taxis and you will get ripped off. Stay away from them.

Exit the terminal and there will be a line of taxis at the curbside - these are the legitimate government licensed taxis. They will charge you metered fare plus a special airport fee. Sometimes you can negotiate a fixed rate.

We took the bus tour of Pompeii two years ago. The whole tour took about 13 hours with a maximum of 2 hours in Pompeii. I learned the hard way. Next time I visit Pompeii, I will probably take the train to Naples then transfer to the train headed directly to the excavation site, purchase a guidebook and roam the sites by myself.

Watch out for young children with cardboard boxes who come and surround you. Their little hands will strip your pockets and purses of everything of value. They usually hang out in droves at popular tourist sites in Rome, especially the Colosseum.

Hope this helps.