I'd ammend my previous comment about cutting it fine, too, given it's a through ticket on teh same airline. You should be fine. No need to worry either, as they're responsible for making the connection.
I can't recall for definite, but I'm pretty sure O'Hare is like most US international airports. You collect you luggage on arrival off the the first flight, clear customs and then drop it off at desks imediately outside customs (i.e. you're not carrying it around), but this should all be explained.