Pre-tour recommendations 3-4 days

Welcome to the forum!
Is this your first trip to Italy?
Sicily is too big and too far for a few days. I would spend your time in Rome if you haven't been there, the tour doesn't spend much time in Rome.
https://www.ricksteves.com/tours/italy/south-italy

I agree with the poster above. You can explore Rome in greater depth than the tour offers. Or visit the areas immediately outside of Rome. There is so much to ecplore.

It’s possible to fly in to Palermo (or Catania) to see a bit of Sicily, then catch a short flight to Rome, but since the tour only has 2 nights (one day, really) in Rome, put in another 3-4 days in rome at the start of your trip! There’s so much you could see/do before the tour starts … check what sights the tour includes, then go to other places within Rome. If you wanted a destination outside of Rome, look at Orvieto. if you’ve stick with just Rome, hopefully the hotel where the tour stays will have a room for you beforehand, and you won’t have to change rooms. Lots more museums and ancient sights to see in Rome that the tour won’t cover, and those would easily keep you busy for 3-4 days. Any interest in Vatican City, while you’re in Rome? Colosseum/Forum/Palatine Hill? Borghese Gallery?

Agreed

That tour only has 1 full day in Rome
Doesn’t include Colosseum, Forum, Vatican, St Peter’s, Pantheon or Borghese

Rome itself needs a good 4 full days
Arrive at least 3 nights before tour starts
You can take a day trip to Orvieto if interested

I'm also in agreement to spend more of your precious time in fascinating and endlessly layered Rome on this trip. Should it be your first RST, it's a real benefit to start off with additional nights in one location and, convenient to add them to the tour hotel. This helps getting over any jet lag and nicely eases you into the brisk pace of the tour. You could/should also consider adding nights at the end of the tour. Out of the 9 RSTs I've taken, Best of South Italy and Best of Sicily are my favorites. Buon viaggio!!