We are leaving for Paris in a couple of weeks.
Can I buy 2 day dual museum pass when I get there to see the Louvre and Versailles?
When I take the train from Paris to Versailles can I buy the train ticket there?
The Paris Museum Pass covers the Louvre, The Chateau of Versailles and numerous other museums and monuments (but not the Eiffel Tower). A two-day pass currently costs 30 Euro. They can be purchased at all of the participating museums and Paris' many tourist information offices including at the airports.
You can get to Versailles by the RER commuter train and buy the tickets at the station. All very easy.
You can purchase the passes at any of the attractions it's eligible for...the Musee D'Orsay is a good place, since there's a separate window at which to purchase passes. They're also available at the tourist info desks at CDG...in terminal 1, and terminals 2 c, d, and f. But if all you're seeing is the Louvre and Versailles, it's not really worth it, at 30 Euro each. There shouldn't be long lineups at this time of year. The Louvre is 8.50 Euro, and Versailles is 16 Euro. But you can purchase a special rail ticket-pass combo for Versailles at any RER station for about 19 Euro (see http://tinyurl.com/y84c3o for more details.) Considering a return trip Paris-Versailles, is about 6 Euro round trip, it'll save you a bit.