Even after buying those double nut ballscrews you still have to mill the parts to connect the nuts to the table.. plus the cutting of the table to make the nuts fit. It's not very simple.. not "ready to put in" at all really. You need the phase2 or 3 motor mounts and whatnot too.
I'm seeing that there appears to be two versions of every ballnut mount, X, Y and Z. The two versions of Y in that folder don't look interchangeable. I mean, one has six holes (but says you need four of six), and one has four holes, but they're not part of the six. I mean, I opened both DXF files laid the four hole piece on top of the six hole version and no holes overlap. The six hole version looks more like my ballscrew nuts. The X axis isn't clear either. One version of the X ballnut mount has pins, the other has holes.
The X and Y motor mounts and spacers are different from the phase 1 I started out with, and he goes to using angle aluminum instead of standoffs (pieces of bar). Instead of four standoff mounts, each motor gets three, but the angle piece acts as a shield from chips and coolant splashes. Instead of using the bearings that come with Griz, he goes over to new bearings, spacers and shims. It looks like he replaces both ends of the X-axis table and uses a different spacer for the Y axis. And, like you say, there's cutting away cast iron in the base to get the ballscrews in place.
The Z axis looks like I can use the phase 1 direct drive mount and standoffs.
But other than that it looks perfectly clear. Easy peasy.
Oh, yeah. I don't see the oiling system anywhere.