There is a shuttle bus from Naples airport to Sorrento- depends what time you land if it's convenient. They also do private transfers.
http://www.curreriviaggi.it/
I haven't used this company myself- just found it through google.
Taxis tend to be expensive around Sorrento- they are the only vehicles without numerous dents!
The town is well seved by bus, train and ferry links. Only trouble with the train is that it means going into Naples first, which might be a bit unsafe, especially at night time.
Hope someone with first hand experience can answer your questions better. It's a beautiful area, I'm sure you will love it.
kate

Unless you are a really skilled driver and are used to driving on the left I would avoid hiring a car.

The hairpin bends in the Amalfi area mean that accidents are really common. I used to live there but would never drive.
The shuttle bus sounds like a good idea I think you can get it at Piazza Garabaldi, but keep your wits about you in Napoli because it isn't the nicest part of the city.

You can get the train on the circumversuviana to Sorrento from Piazza Garabaldi train station in Napoli.
As for Ravello, I think there is a bus from Sorrento to that area. Check when you get there as there may be better options.