Hi. Jim, Hmmmm. Where to start! We all owe you a lot IMO for your help, so please keep on asking! My take is you have 2 options. Go OTS and just pull down Cura. It is fine for starters as a slicer. My sense of a slicer is software that takes an STL file and uses particular printing routines and options to develop 3-D printer g-gcode. An example would be the infill style and density. A 20mm square STL File test block is pulled into Cura. You throttle the exterior to be a 3mm solid outer printed cube material. Then maybe 15% infill. The infill percentage runs a grid pattern internally to fill the void of the remaining 17mm of space.
Take that up a notch. Pretend you have a long overhang or some gap in the center. You need to print support structures in and around holes and bridge points. You then need to pull them off easily. Perforations, tear outs, etc. You often need to set the offset heights for supports to keep them from sticking too much, but enough to keep it from warping and sagging as well. And the better the software, the better all those specialized 3D nuance routines will be. Cura is good. It is free, and does most of what ya need. We quickly moved up to simply3d for $149. 2 seats. My kid and I LOVE this package. The gcode that a slicer gens is so full of all this nuance and specialized code that I just scratch my head at how someone can come up with some of this stuff.
Mitchell is doing a 3D prototype of a lamp for his design school. The 4" bolt holes all have internal support prints inside the holes to keep them uniform and crisp. When it was done, I pried up 1 end and the way they printed this infill was incredible. It came out like a zipper.! One long folded 3D printed infill for a long hole. Many know what I mean. You get melting , bad infill that is too dense, or not able to stop warping ... That's the kind of thing I mean by a top notch slicer. 20seconds and my 4" 7/16 holes were unzipped.
Headed bed.... No brainier. Do it! Kits abound out there. For materials, fumes and such for me left us using a product called nGen. Tough, and little to no warping. Pla is fine too and very inexpensive compared to some products. When you get into the nylons, you need higher print head temps. So you need a system to drive the higher temps for the material and you need the heated bed. I love the Taz6. Overpriced but you print out of the box. All of their source, parts, and manuals are on their site. You can make a taz6 with any 3D printer. True open source so they say.
All fusion 360 does is take my 3D part and convert to STL and launch my slicer program. From there it is all about Your slicer spitting out gcode based on tricks for printing objects via a fluid.
If you make your own, you will need something to also feed the filimrnt into the head. That feed rate is adjustable in the slicer software but usually is not tweaked. Maybe consider possibly buying a unit that you can tear down and put discrete modules into your cnc setup. The head and feed motors onto your Z setup? Again, The taz6 is run by the arduino or something like thT. All firmware is open for you to pull down. Buy a head end, Plug it into Cura via a USB cable, calibrate, set the type as taz and you may be close? Lol. Yeah. Sure...