I live in Paris (well, near Paris), and all I can say is : Do not attempt to drive a car in Paris. I've lived here for 12 years and I'm still scared each time I have to go through the city. For someone who never went there, does not know some of our most peculiar traffic laws, it's just cheer madness.
Luckily our public transportation is very nice, if a bit stinky at places (this is due mostly of some type of rock underneath Paris, and not because french people don't wash
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
). So take a full subway pass for the length of your stay in the city. Just make sure you take one that allows you to go outside Paris if you plan to do so, like going to Versailles or even Disneyland (not recommanded this time of year, it's horribly cold, I live right next to it so I would know).
As for what to visit, people already recommanded the usual places, Eiffel Tower, Arc de Triomphe, Le Louvre, Saint Chapelle (a must see) and Notre Dame, Champs Elysées, you name it. For more modern art there is Beaubourg, La defense is nice to go see if you have 2 hours to spare, and of course there many smaller things to go to.
Enjoy your stay, just make sure you stay out of Subway at the big hours (7-9 AM, 6-7 PM), it's a nightmare especially if you have big bags with you and are not used to how it all works.