While living four years out in the western suburbs (Westmont, IL), my wife and I often rode the train (CTA) into Chicago to site see, see a play, or shop. Parking is available for you out in the Chicago burbs and the train is safe, fun, and convenient. The cost to ride is reasonable as well.
I would not advocate driving any type RV into the city due to traffic congestion, very expensive parking rates, and lack of any type RV parking. No, can't suggest you attempt to take a TC downtown.
Chicago is a great place to visit. Much to see and do there. As others have suggested, you should avoid the citys south end for safety reasons. That said, Chicago is no more or less safe than any mega size city in the U.S.
Do some reading about the city sites, make some plans relative to parking and public transportation, and enjoy a great american city.