How is the unit controlled? Is it a PC running with a special card or just from the parallel port? I doubt they wrote the control software themselves. If it uses a serial port (or possibly a USB) it may be a Flashcut based unit and that software can be purchased easily. I have not heard of WINPlasma software but if it's another brand just repackaged (OEM) you should be able to find it.
If it works great, sounds like all you need is a manual(?)