Yes, pre-planning is necessary for any European port if you are going to do it yourself.
In this particulare case, if I were to do the cruise again (could happen), I would probably "miss the ship" and spend a night in Cinque Terre. Livorno is the next stop on the cruise and only 1½ hours by train from CT. The only downside being is that I'd miss the first formal night of the cruise.
Radiance of the Seas - Nov 2006
Legend of the Seas - Jun 2007
Costa Fortuna - Mar 2008
Legend of the Seas - Oct 2008
Celebrity Constellation - July 2009
MSC Orchestra - Jan 2009
Navigator of the Seas - March 2009
MSC Poesia - November 2009
Jewel of the Seas - June 2010