I did just the same thing- a quick three-night trip, mostly to see the Monet exhibition.
It was FABULOUS !! I wish I had known about the Carte Sésame, though; we waited in line for 2.5 hours!
We also saw the Trésor des Medicis exhibition at the Musée Maillol, which goes on until the middle of February. Worthwhile, but nowhere near in the same league with the Monet.
Have a great trip!