I spent two weeks in Sicily two years ago that included four nights in Palermo. Loved Palermo. It is a good walking city with plenty to see. One of the main drags is Corso Vittorio Emanuele, about four blocks north of the train station. The Fontana Pretorio (nearby church) and Quattro Conte are just west of Via Roma. Those are both quick. Keep walking west and there are some cathedrals and a bit further is Palazzo Normanni.

I almost forgot, the catacombs are a bit further out and that was a memorable visit. It is unusual to say the least. Most of the bodies are mummified with period dress. I have been to catacombs elsewhere, and these are by far the most interesting and unusual.

Some of the markets are fun to visit. Palermo has an archiological museum that is worth a visit. Cin Cin is a great restaurant. We stayed at the Ambaciatori Hotel on Via Roma which has a fantastic rooftop terrace for evening cocktails with views.

Messina is too far for a limited visit. Cefalu is about a 30 minute train ride to the east and is a small fishing village worth a visit, time permitting. I suggest a good map of Palermo that lists the most important destinations. Let me know if you have further questions.