Katie -- Happy Birthday! From your description of what you love love love, I think you should just move to Paris. ;-)
Start with "Explore Europe" above in this website, and also look at some guidebooks to figure out what sights you want to see most. Be selective, even though you're giving the city a good week you won't see "everything." And you're definitely right to leave some down time for strolling, cafes, parks, etc.
Assuming that you've already got air travel arranged and a place to stay, the only other arrangements you may want to make ahead of time would be that birthday dinner and maybe an advance ticket purchase for the Eiffel Tower. I can't help you with either but others on this board can. If you're not getting useful responses, try posting more specific questions about restaurants etc.
One thing no one's mentioned is a Seine cruise, something I'd strongly recommend on a nice day or evening (or both). You don't have to plan ahead for this, they leave every hour or so from docks near Notre Dame and the Eiffel Tower. So you can time this based on weather and when you'll be where. I wouldn't recommend a dinner cruise (which you probably would have to set up in advance) simply because your dinner would be competing with the views for your attention. Are you going to look up at the floodlit monuments or down at your plate so you don't stick that fork into your knee? ;-)
I agree with Janet about St-Denis and the Promenade Plantee, if you want more than the usual old standbys. Many people go to Versailles, which will take basically a full day for the palaces and gardens. Another good day trip, if you like cathedrals, is Chartres. But don't overdo it -- you're only 30 and hopefully will have many more chances to visit this magnificent city. Or live there!