Italy Nov 08

So this is my first time doing any thing like this. I am planning a trip to Italy I have wanted to go forever. The person I am planning the trip with may not be able to go so I have been looking into my other options. The plan is to leave after work on Nov 12 and get into Rome Nov 13 then take the train straight to Paris. Spend the 1 day there and take the train back into Italy and go to Venice. I will then work my way down south all the way down to The Amalfi Coast. I will be spending 3.5 weeks there. If any one has any good advise please let me know.