Going in/out of Sheraton CDG

We booked the Sheraton in the airport for a layover from LIS>CDG>LAX. We are flying Air France which I was told is just a 5 to 10 minute walk to the terminal. My question is if we leave the airport to go do some quick sightseeing what is involved in coming back to the hotel and how much time would we need? I have not stayed in a hotel in an airport so wondering how the process of coming and going works.