Paris is ridiculously easy to get around. Buy a 3 or 5 day pass and you will make your money back in 2 days. We even used our 5 day pass for the funiculaire at Montmartre, bypassing a huge line for tickets.
We used the Tube 2 app on my smartphone with the Paris and RER maps, and never got lost. The app shows your route, changes, directions of travel for each train and written instructions that are easy to follow. Works for all of Paris.