and now my head is hurting
youll get a lot of that.... broken down, a cnc router is a little less rocket science however you are at the difficult stages of looking at cnc as a whole... all the options! (not easy)

if you have the time, inclination and the gumption (and enough cash) you will get there

if you are going to exclusivly cut foam you wouldnt need a big sturdy machine however im guessing that if you are going to build a cnc you may as well go for glory and build it to cut a range of materials (plastics wood and small amouts of soft metals is the usual script)

your brain will hurt at first but dont be in too much of a rush and do lots of research, the build logs on this sight are a good place to start

good lock :)