Hi Lynn,
You will love the Galaxy... very pretty ship and very easy to get around...
to (hopefully) answer some of your questions... usually you need to be back on board about one half hour before sailing... the trip from Livorno (where the ship docks) to Rome is about one hour. The process of getting off the ship is very smooth.. (except on disembarkation day)... but in ports you will have no trouble.. as long as you have a picture id and your sail card.
Before our trip we toyed with the idea of using local guides to show us around rather than using a ship excursion due to the high cost of the ship's excursions. We even emailed with a couple of tour people requesting rates, etc... but after serious discussions we decided to use the ship's tours just for the fact that should there be trouble on the road, the ship will wait for you as long as it's one of their tours. If you are on your own, it will be your responsibility to meet the ship at the next port if you miss it. We just didn't want to take the chance.
Dubrovnik was a stunner for us... truly beautiful walled city... ceramic tiles on the walls of the houses... marble for streets... very beautiful.
Please don't miss Santorini... we were staying late in port.. (i think around 11 PM) so we decided to stay there...and have dinner at one of the local restaurants... it was the best night... gorgeous sunset, greek music playing throughout... and a wonderful open air restaurant overlooking the bay... we didn't want to leave.
Not sure what your likes or dislikes are.. but i found Pompei fascinating.. to see how they are still uncovering this buried city is amazing... and to see the bodies of people and animals was incredible.
the rest of the trip was wonderful... our trip of a lifetime... and you will be doing it on a gorgeous ship too...
Also, if you're interested.. i have a photo gallery of our trip in the gallery section... it's labeled "Millenium-Mediterranean 10/03.
Anything else, please let me know... i'm happy to answer
Frank