You could follow the wires and pcb traces from the motors back to the ic that controls them, then find its datasheet and go from there, but its probably a long tedious job to reverse engineer.
Might be better to pull all the pcb's off it, and connect to the motors direct and use something like an arduino to control them, there might even be a library for it, you'll need some kind of position feedback, but there probably is something there allready for that.
In fact if you just want manual control you might evenget away with wiring the motor to a joystick or 2 dpco switches and no electronics.