Hi Travis, sorry for replying a bit late.
The slider is built on standard industry Alu profiles (40x40mm) with 8mm gutter.
Power is delivered by a DC motor (not step-motor) continuously. A small and simple gearbox is built in.
Power is transmitted by a 6mm screw, nothing precise, just a threaded industry stick. It all appeared to be very smooth in motion.
The rest of parts is custom built. Check out m entry blog dedicated to this device, where you can find most of the technical details.
Overall cost was approx. 300-400$.
http://lederfotoblog.blogspot.com/2012/08/motorized-timelapse-slider-building-and.html