Florence is possible from La Spezia but not if you want to see Pisa. I would avoid ship tours as they will most times stop at a leather store and eat into your time. We use Rome in Limo. It is expensive compared to ship tours. $750 euro gets you a private Mercedes and English speaking driver/ tour guide. They can navigate the city for you and take you exactly where you need to and want to go and no frivolous stop at a sponsored store.
By car it is about an hour and half to an hour and 45 each way. Should get you about 5 hours in the city. Get the lay of the land, see the highlights and then go back and stay longer if you fall in love with the city. (and you will)
In Santa Margherita you can either to Portofino or Cinque Terra. I prefer Portofino and you can do both if you get a private tour.
Language is not a problem but I would learn a few greetings like Buon Giorno (good day) or buona note (good evening). Avoid Ciao as it is used more for if you are familiar with the individual (casual greeting) Ig you at least try the language they will know you are not Italian and speak English with you. Same goes for France. It is more important in France to at least try a greeting from my experience.
Amalfi Coast when in Naples is our preference. Either ship tour or private. Rome in Limo was our choice last trip. Ship tour stops at a broach factory. Not our thing.
Good luck and have a fabulous time.