Italy
 

We plan to go to Amalfi and Sicily next September.
1) Do we need car service and/or a guide to go from Pompeii to Herculean and then to Sorrento?
2) We plan to go from Catania to Taormina for the day - do we need car service and/or a guide or is it doable on our own? We also would like to visit Mt. Etna from Taormina. Do we need a guide and/or car service, or can we do it on our own?
We are in our mid sixties in good shape.

None of these require a car service or guide, but whether or not you choose to use one depends on a lot of factors. Most important is your own travel style.

- your desire/ease/familiarity with using public transportation (train and/or bus)
- are you doing day trips, or will you be schelpping luggage on these routes
- your desire to rent a car or not
- budget

If you are staying in Sorrento, you can hop the local Circumvesuviana train to Pompeii or Herculaneum (30-40 minutes from Sorrento - 2-3€).
http://www.vesuviana.it/web/en

At either site, you can join a tour, find a guide or just rent an audio guide.
http://www.pompeiisites.org/

If you meant the first question as asked, then no - there's no real need to use a car service.

Sorrento is on the same Circumvesuviana line as both Ercolano Scavi station (for the ruins of Herculaneum) and Pompei Scavi (which most people use when visiting the site there)....

http://www.pbase.com/isolaverde/image/128288647

Between those two sites there's a third that might also be of interest - known as Poppea's Villa, at Oplontis - for which you get off at Torre Annunziata:

http://www.pbase.com/isolaverde/popea

It's only small, and wouldn't take more than an hour...

Peter

Consider taking a side trip to Castelmola (a small village overlooking both Etna and Toarmina) - it is magic

There's a nice train from Catania to Taormina/Giardini Naxos station, from which you can get a taxi up to Taormina. If you want to go to Mt. Etna on the same day, then you probably need a guide to drive you. It's possible there are bus tours that do both?

Any particular reason you're staying in Catania?