I recommend getting tripso (then download the Paris maps) for your iPhone as it will pin-point most of the destinations of interest. It's also free and can be used offline, I believe.
The Paris metro is a little confusing but easy when you know where it goes, so I suggest reading
on about how it works. The temps are much warmer than Chicago at the moment, so whilst you might need a long sleeve top, raincoats are good enough, no need to bring thermals (about 12-13C atm).
I'll leave it to the others to suggest some good places to visit/eat as its been a while. I didn't run out of finding things to do there without an itinerary though, I just grabbed a map (pre-smartphone) and walked/metro'd it.