The drive usually takes about 7 hours (with stops for food, gas, etc.) from downtown Chicago. However, we drove two weeks ago, and it took us 7.5 hours because we hit construction on I-55. So you may want to plan 7.5 hours, if you're being conservative. The general route is:
There's construction on the Dan Ryan (I-90/I-94 south of the loop) and The Edens (I-94 north of the city). Your best bet to I-55 is I-355 from the north or Lake Shore Drive from The Loop.
The only tricky part is MO-370 around St. Louis. Here's a detailed map:
View Larger Map (ignore the written directions)
Here is the address for Les Bourgeois, where the ceremony and reception are:
Les Bourgeois Blufftop Bistro
12847 W Highway BB
Rocheport MO 65279
The Les Bourgeois website has directions and a map. Do not use Google Maps, as it does not know this address. Use Yahoo Maps, instead. The Blufftop Bistro is about a mile from I-70 on Highway BB the left-hand side of the road. Don't be fooled by the market, just off the highway, on the right!
The gallery is in downtown Columbia, off the main street:
812 E. Broadway
Columbia, Missouri 65201
You may find street parking, but there is cheap parking in indoor lots a couple blocks away. For detailed directions, Google Maps or Yahoo Maps should be sufficient.