Chicago Here I Come!!!!

My husband and I are planning a trip to Chicago and I couldn't be more excited! I have heard such great things about the windy city and I can't wait to get there to explore for myself!  Does anyone have any suggestions for while I am there? My friend that travels to Chicago for business said that I do not need a car and that I should stay somewhere near the area of the Magnificent Mile/Navy Pier. I am open to other suggestions as well!  We will be there for about 4 days and I am trying to get tickets to a Cubs game (and to Oprah but what are the chances of that...)  Can't wait to hear your advice:)