Most of the metro stations in Paris do not have esclators or elevators, so you will have to carry your luggage up and down the stairs. Just be wary of pickpockets, and keep your eyes/hands on your bags at all times!

It is easy to go back from GDN to CDG, and probably takes no more than one hour (45 min), and costs about 12 dollars per person. Make sure you take the RER-B train, and that you know which terminal your flight is leaving from, as there are two stops on the RER-B for CDG.