For the motor itself, look at converting a DC motor to servo.
http://truetex.com/servomod.htm You can select any size motor you need
then. For your application this will work great.

lots of servo control packages out there. One option is to use Advanced
Motion Control analog servo amps and a Galil computer on a PCI slot. You'd
need a way to mount a PC inside your machine to go this route. (Only the
motherboard, galil card, and hard disk while machine runs - plug in keyboard
mouse and monitor to program) This would also give you a bunch of I/O
capability in addition. I'd shop eBay for these items.

Karl