I am just finishing up a Mach 3/Galil 22x0 conversion on a mid-80's mill with DC brush servos. I don't think the amount of work is much higher using individual components than buying a complete system. You load the Mach 3 software and Galil plugin, run an ethernet cable, plug in the breakout board(s), and the controller is done. The work is interfacing your existing drives, motors, limit switches, relays, etc. None of this can be plug and play unless you are buying a control for a very specific machine.
I am using a touchscreen, but have kept external buttons for e-stop, cycle start & hold, and pots for feed rate and spindle speed. I am also using a pendant with MPG. My machine has a tool changer, so I am using a PLC for that.