Hello rcbbailey, and welcome to the forum,
Some of what I think is missing from your question is the number of nights you're intending on staying and where.
As others have said it is a bit of a trek from Lake Como to CT and this will probably end up being 6+ hours on the train to make this happen. Given that I would suggest at least 3 nights in CT - that gives you two full days to explore because you are going to arrive probably late afternoon on your arrival day at best. And if you want to make a day trip to Pisa then make that at least 4 nights.
It's probably about 1:30 on the train to Pisa one way and the train station is a ways cross town to the Field of Miracles. You could take a bus, a taxi or wander across the city depending on what kind of a traveller you are. Just be aware you need to cross the river so pick a route that crosses a bridge. I'd probably suggest walking over and then deciding if you feel like getting a ride back to the station. Read up on the process of getting on the list of going up the tower and I would recommend leaving as early as possible.
The train from La Spezia to Nice is probably 6-7 hours on various trains. Check your train options but crossing borders often involves changing trains. Monaco is close enough to Nice I would suggest pushing past Monaco and onto Nice to store your bags and get settled. Then visit Monaco unencumbered. Antibes is another great place to visit from Nice.
Have a great trip,
=Tod
