First point: Here's a hint - you've described that the PCB is nothing like any other photo of PCBs... so we're as blind to this as you are. Take a good hi-res photo of the PCB and post it here.

Second point: Mach3 - I hate it (mainly for the ye-olde windows experience) but it is fairly straight-forward and there's plenty on here that know it well... better/more than any freely available alternative. I'd stick with Mach3 for now (provided that you have a machine that runs it). There's plenty of tutorials online and if you invest a bit of effort then people here will typically help.