Quoted from rosh:You can take a train directly from ohare to wheeling, however that line has very few trains compared to most of the train lines in Chicago, in the afternoon there is a 1:30, 3:30, 5:00, 5:25, 6:00, 6:25 and 7:30. You do have to take airport transportation (both a tram and bus) to get to the "o'hare transfer" station. Wheeling station is about four miles from expo so you would then need a über or cab.
Actually, I have walked from the Wheeling station to the Westin several times. It's more like 1.2 miles if you use the shortcuts. The hotel runs their own shuttles to Lake Cook station (Milwaukee District North line, to Fox Lake) on demand, and I think they would go to Wheeling station if asked. (This service is only available to hotel guests.) I agree that the North Central line has relatively few trains.
.................David Marston