[Alan Anderson]

Reading the OI potentiometer is easy -- just connect it between +5 and one of the OI analog inputs (x, y, wheel, or aux) on a joystick connector.

But without a position sensor on your turret, you won't be able to do much with the value coming back from the OI. How will you know which way to drive the turret motor if you don't know where it's pointing at any given moment?

If you don't have room for a pot on the window motor, how about putting a gear on the shaft it's turning and putting the pot on a matching gear connected to it?