Just completed my one week to Paris. It was great, though exhausting. I was worried about the issue of pick pockets. Believe me, its over rated. I had absolutely no issues. I travelled every where using metro and RER . The tickets are easy to buy using the automated machine. It had english language option. The staff at ticket information talk in english and will guide you about the Paris zones.
Don't worry about the pick pockets. Follow your instinct. I also used 'Batobus' for river siene.