Using AX500 to control a Brush DC motor into a big servo

I was wondering if I could use the AX500 to control a Brush DC motor into a big servo so that I could have the motor come back to center for a steering motor?? ( I am using a RC to control the steering)
If yes would I use a potentiometer of an optical encoder to tell the position of the steering?? (to come back to center when the RC stick is in the middle)
If yes would you be able to provide me the right encoder??

You can use a pot to give position feedback. This is preferred to an optical encoder because pots give absolute position information (they are much cheaper too).