Welcome to cruise-chat, and congratulations on your upcoming cruise!
I agree with janfred. Century is a beautiful ship and offers lots of amenities. Please don't be concerned about her age -- at 15, she's far from being old. She's been refurbished several times over the years, including the major refurbishment to which janfred refers. She's also an excellent ship for a port-intensive cruise as you are taking, as her relatively low number of passengers means easier disembarking at ports and a less frenetic pace onboard. We were onboard for a Northern Europe cruise in 2007 and I give the ship and her crew high scores all around.
You have a super itinerary. I'd suggest checking out our Europe Port Chat forum, located here
, including a very informative thread on train travel in Italy.