You should get a toll reader with the car. You will end up on a toll road at some point almost for sure. If you don't have one and you miss paying a toll, there is usually a sign after the toll booth with a url where you can pay and avoid a hefty fine - compounded by the rental company's fees.
Driving early in Chicago on a week day means driving in traffic. Parking is often hard to find in neighborhoods. Traffic around the ball parks gets pretty bad before and after games. Allow enough time. I haven't been to Oak Park for 2-3 years, but I remember finding street parking. Watch the signs - some is for residents only. There are several options for a Wright visit. Book a guided tour of the home and studio in advance. I've done neighborhood tours thru the Trust, both guided and self-tour (with map and audio guide). There are a number of Wright homes in Oak Park and a church too.