The weather in Sicily should be pretty good in November. We did the RS tour last November ending I think about Dec 1. A couple of places it was cool (but not cold) but that sure beats the summer heat of Sicily! Take a light jacket of some sort as it might be a little chilly by the seaside at times.
A few observations from our trip:
1) We stayed several days in Palermo and in retrospect I would only spend a couple of days there at most. It is interesting but It tends to be very loud and bustling, and we found it tiresome after a few days with the constant noise. Not at all a relaxing place. That said, after you see the Cathedral and some of the typical sights make sure you visit the Mafia Museum. Very interesting on the history of Mafia and the mafia wars of the 70s/80s.
2) Your choices for flights into Sicily are Palermo and Catania. Lots of flights on ITA from various Italian cities. We flew into Sicily and out of Catania. The airport in Palermo is about 25 or 30 miles from the city. Take a train or bus into Palermo. The train worked well for us (several stops and will take about an hour) and was relatively easy from the platform downstairs at the airport. I can give you more details if you like.
3) We did the RS tour so I can't give you suggestions on driving, other than there is absolutely no way I would drive myself. Some of the cities you probably want to visit such as Syracuse, Taormina, and Trapani are difficult to park or access by car easily. Probably would need to leave car outside historic area. On the RS tour we were often dropped off outside the historic areas and took taxis into our hotels as these areas are chaotic. So I would equate having a rental car with major stress and a hassle. I would suggest the train to be an easier form of transportation (although a tour is by far the easiest way INMHO). But should be able to most places by a combination of train and taxi. Possibly rent a car in some areas for a day or two.
5) Iten: I think using the RS tour as a template would probably be pretty good and you can add days to slow the pace over a tour. My thoughts on cities/destinations:
Palermo - Two days here is fine. A loud and hectic city and we spent probably 5 days which was about 3 too much. Go see the Mafia tour, we found it fascinating. The Cathedral was interesting as well as the rooftop climb has a nice view. A few other sites easily done over a 2-day period. Stay near the train station to make it easy to arrive from the airport (or leave) by train.
Trapani - Interesting seaside location. Nice to walk around for a day. The tour also took us by boat to a nearby island (Isola Di San Pantaleo) which was interesting and there is a seaside salt processing mill. Nice little city to stay for a couple of days.
Agrigento - The valley of the Temples is very interesting. It is an archaeological site and museum area.
Syracuse - The historic area is really cool, but as I mentioned you pretty much need to take a taxi into the city as even if you can drive into the city there would be nowhere to park. City felt very old world, and we stayed at a hotel that I think was previously a convent. The nuns worked the place.. I'd spend 2 or 3 nights here as it was seaside and nice to walk around.
Taormina - Definitely a gem. This is a resort destination with lots of nice shops and restaurants, but by far the nicest city we visited. I'd spend a few nights here. Another city that would be difficult to part with a rental car. Probably have to leave it outside the city somewhere.
Mt. Etna - If you have a car worth a stop and walking around the craters.
Catania - Skip it, Dirty and crowded city. If you are flying out possibly stay at one of the hotels near the airport.
Food - Was great everywhere.
My $.02. Happy to answer any more questions or specifics :)