Hi...you can take the train from the port...about a 5 minute walk...to Rome. Once in Rome, you can meet with your tour guide. Private tours are more expensive, but well worth it. If you can get a group of about 6-8 that would be great because it's small and you can share the costs. Go on the web and search for Rome Day Excursions, you'll see plenty of them all varying in costs. The train schedule can be found and tickets can be reserved at www.trenitalia.com
Cost is cheap! firstname.lastname@example.org
is a good contact...highly educated American guide. Hope this helps!!!