Okay I want to keep this shortUsually the worst way to get accurate answers.
How would I hook A PC steering wheel to arduino.Is it a USB device? If so you either need a USB Host Shield (or equivalent) or you need to rip out the USB electronics and hook the Arduino directly to the sensors.
Then would I hook that to an rc car to be controlled by the steering wheel?Yes, you probably would. It sounds like you want to. I expect that to do it you will need a transmitter that matches the receiver on your RC car.