I might actually prefer Musee D'Orsay over the Louvre, but both museums are something you don't want to miss out on when visiting Paris. The lighting of the glass roof in the Lafayette warehouse during Christmas season is unbelievable. The stairs up Montmartre are the real experience, and just catch the comfortable funiculaire back down again. Don't leave Paris without seeing Versailles! As for day trips from Paris I can highly recommend Rouen! Most idyllic medieval city I've been so far.