You can't connect any motor (servo or stepper) to the parallel port. You will need to the a driver board for the stepper motors. You can go with the Gecko G201's or other stepper driver boards around. I would stay away from the Unipolar boards and get a bipolar chopper driver (more power).
In order to tell about the drive system you will need to know more about your Vexta steppers. Tell us how long they are? I have some Vexta steppers as well.