The OP is coming from the south, so campgrounds south of the city are the best bet.
Indiana Dunes is close (50 miles east) to the city, there is the
South Shore train stop right at the park entrance, it is about 1 1/4 hours from Dune Park stop to Millenium station, it also stops at the museum campus.
Plus, the Dunes is worth a day or two of exploration there, beautiful beach, trails, etc.
From Millenium station, it is exactly a 1 mile walk or less than 2 mile cab to Willis (Sears) Tower.
Navy Pier is less than two miles to Millenium Station.
Wendella Boats offers really cool tours of the Chicago River and Lake Michigan (sunset tours, architecture tours, fireworks tours, etc)
Here is a tip, if you take a cab back to Millenium, tell them to drop you off short of the station so that the panhandlers don't harrass you as you get out of the cab.
If you are interested in the Museum Campus, the
City Pass is a really good deal, and it also gives you admission to the Skydeck at the Willis.
As others have mentioned, driving a truck in parts of Chicago is prohibited, parking is just about impossible and super expensive when you find it, and traffic can be just about gridlock, especially on weekends, during the Taste, and when there are ballgames at either US Cellular or Wrigley.
