Your question was where to start
I think the thing to do is download Mach3 first into a computer - do not worry which one. I assume you already have a lathe - although you do not say how big it is. I dont how big the ducks are that you are calling. Have a look at Mach 3 turn and go through the tutorial videos and try and relate the videos to Mach 3. You should try and understand how all the bits work in relation to the lathe, and identify most of the features that you use on the lathe and try and uderstand where you can benefit with CNC.
Once you have done that, the only two things that you have to bother about is - the speed of the lathe spindle and - driving the axies. I use my lathe for metal work - miniature railway parts - so speed control was a feature I would like to work. I got hold of an Omron single to 3 phase inverter and a three phase motor from my brother in law. This controls the spindle speed, although I might have a bit of trouble hooking it up to the computer, because the Omron is an old model and not really designed for it.(£20 the pair)
The other problem is the stepper drivers for the lathe axies - how big do they want to be, and although you can read the spec of them you have no idea what that means in terms of performance, because I have no idea what a Mn or Nm is. I bought a stepper driver from a shop on e_bay and hooked it up to a stepper motor I had in a kit I bough some time ago. (I would has used the original driver but it was a serial output instead of the parrallel output that Mach3 needs), and I have fastened it on the lathe cross slide, driving the cross slide spindle through a 5 - 1 reduction set of toothed pulleys. This seemed to be the simplest way to start.
I got an old printer cable and cut it in half and made a board out of copper clad to access all the wires out of the plug, identifying each with a multi meter and then linked this to the stepper driver. I am driving the stepper driver with a pair of 12 volt (i.e. 24 volt) batteries from my mothers old wheelchair ( She said it wasn't fast enough and insisted on buying a pair of new ones - so I got the old ones - ideal for experimentation). I hooked all this up on the workbench and tested it. I fastened the stepper motor to the driver (which wants to be well out of the way of the lathe) with a length of four core 10 amp speaker wire and a lockable plug and socket so I can take the computer in and out of the workshop as I need it.
I tested the stepper motor on the workbench, fastened to the computer, running Mach 3, and using one of the macros already in Mach 3 and watched it gaily rotating backwards and forwards as it followed the G code program. You can alter the parameters and watch the motor respond, which helps in the understanding of the program. I felt very satisfied.
So far my outlay has been about £50 ($100).
I am getting a toothed belt from the manufacturers today to connect the motor to my lathe cross slide, so I should be able to test wether this motor has the power to drive it - if it has all is well, if it hasn't I have been looking on the net for another motor and seem to have found one that is twice the power of this one, for about £20 - but I can use the same driver - and if that one a too small, then I will have to take the plunge and buy a bigger motor - but I will also need a bigger driver!!!
Once I get the basics right, I will bother about the right computer, the right limit switches and all the other bits and pieces - the lathe has a milling attachment - so I can have a go at that as well.
I got the bug by going to a local CNC workshop for wheels and axles for the railway ( I bought 160 wheels and 80 axles) he had them all done in two days to my spec - and all were identical - I can put any wheel on any axle - it is a perfect fit and leaves the 2 thou gap for the adhesive. He also cut, out of solid bar, a gearbox item that took me a full day to make - and charged me £6 (I got 50 of them) - this is a great increase in productivity - and if I can emulate that for some of the smaller items on my own lathe I will be very pleased.
Hope this gets you started.
Jim Pinder
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