First of all, there's a reason Francois is a Superhost: his communication was outstanding. In addition to being available day or night to answer questions, he provided an extremely detailed information booklet with everything that a guest might need. Bravo!
The apartment is on Level 1 (that's the 2nd floor for you Americans), up a short staircase. There is a small lift available, but we didn't use it, so I'm not sure how effective it is. Francois offered three sets of keys which was very handy for our group to have. The apartment was as advertised with 3 bedrooms and 2 bathrooms.
As others have said, this place is located in a pedestrian area, so you must walk a minimal distance to reach the apartment from the street. Both Chatelet and Les Halles stations are extremely close and convenient as were other attractions in this part of the city.
This is an area with several bars and restaurants, the patrons of which you may encounter after an evening out, but once I entered the apartment I never heard any noise from the square below.
Thanks, Francois!