I would like to hear your ideas on a delta printer! That’s exactly what I have been researching for some good use for the cnc mill! I haven’t found any good designs yet.
The 3d printer is the hard part compared to getting a router working. Its just like 3d printing, except your tolerance for zeroing out machine on the work surface is much easier. I would recommend estlcam starting out. Easy to get some tests going. I also recommend using the “universal mount” for extra z rigidity. It helped out my prints greatly using this also! The slower I print, the better they turn out. Adding the heated bed was absolutely worth it, and improved my prints a bit more also. For less than $35, it was totally worth it. ($18 power supply amazon, $12.99 heated bed with wires and thermistor already soldered on, also amazon)