CNC newbie looking to convert commercial engraving machine

I'm based in Suffolk and was recently given what amounts to a complete workshop, lathe, milling machine, literally tons of tooling, and a non-functional computer controlled engraving machine. The engraver is a Suregrave Rotation S and although it appears that the steppers and spindle are in good condition, the controller does not work. These machines had a bit of a reputation for being uncooperative and flaky in use and the manufacturer has long since disappeared so no support available. I have been in touch with someone who is an acknowleged expert on Suregrave stuff and his view is that it would be very expensive to repair and a better course of action would be to put together a new controller system.

I have very little knowledge of CNC systems but a good grounding in both small scale engineering and basis electronics. I'll be looking for advice and recommendations to enable me to convert this beast into a functional engraver. I'm not sure where the boundary is between straightforward engraving and CNC routing, I suspect the boundary is a bit blurred, but I'm assuming at this stage that this sytem could be controlled by Mach3, which has an engraving module, but I'm open to other suggestions!

Gordon