If you can hook the potentiometer up to the shaft of the steering that would be your best bet. There are different type of potentiometer including Limitless and just single rotation. Both of these can be hooked up to your Analog input to tell your angle.
http://www.chiefdelphi.com/forums/sh...=potentiometer
You could also do it with an encoder also. You have your starting position call it zero. You count the pulses if you go left or right on the sensor. Then when you want to return you just do the opposite back to zero again.
The easier would be the first option with a potentiometer on the shaft. If you need additional help with programming or something feel free to contact me on IM.