I lived in Paris from 1986 to 1997. Got my OM-3 brand new at that time. I started using it again 3 years ago after being fed up with watching a computer screen for my photography. I do the latter all day long for a living...I still have loads of negatives from those days. They have all kept well.
I never had a problem photographing anywhere in Paris. Obviously, museums and public places have rules - like anywhere - which are usually clearly posted. Common sense goes a long way. You wouldn't be setting up a tripod and huge flash inside the Louvre, now would you?
There was only one time where I felt a bit uneasy taking pictures: 14th July 1989, early morning, I made a point of driving around town "documenting" how the city was waking up to the festivities and ended up among a bunch of Nationalist skinheads, all balaclavad, gathered around the Jeanne d'Arc statue. They did not want to have their picture taken. Usual and typical cowardice that can be expected from fanatical extremists of any so called cause...now, the funny thing was that just a block away, there was a large gathering of riot police - the CRS - and they were even more upset about me taking pictures! I had to ask my then girlfriend, later wife, to step on it, or my beloved OM-3 would have permanently changed ownership at that time... Nice memories at any rate - and my own doing.
Have fun in Paris. I will also go there later this spring. Will I bring the OM-3? Mais bien sur!