Go to
www.nissan-techinfo.com
You'll need the $20 one day viewing subscription, and a fast internet connection. You can open each section of the FSM as a .pdf and then use the "save a copy" button in Acrobat reader to save it section by section. You can also download the TSBs and FSM for your Sentra.
I bought the one day subscription and then went on a download marathon for 24 hours (slept for four or five but not much), but I got several FSMs for cars I have (and ones I would like to have) etc. You should be able to pull it off in a few hours if you're only dealing with one car and have a good connection.
Heath