Most cultural place I've ever been to
Don't get the metro pass because it's nicer to walk. Every corner you turn will have something new to see. It's not far from each other. Get one of the free maps and draw out where you want to go and just do it. It's very easy to navigate around this city even if you don't know much Italian.
Insider Tip:Eat as much as you can but use the travel guides because they give you a pretty good idea of how good or bad a place is. I haven't been disappointed in going to a good rated one.