The process looks relatively simple on the paper: just replace the cutting tool head with an extruder, and optionally add a heated print bed. The extruder is the part that extrudes melted plastic to form the printed object. The heated bed is needed to eliminate warping of the printed object. Without the heated bed, the bottom layers would already be cooled when the top layers are printed, resulting in warping and lifting of corners away from the bed.
First there is a picture of the completed conversion, and a few printed object in the foreground. The extruder is behind the wooden block which holds it in place. The heated bed is the red piece on the bottom, and on top of it is a aluminum sheet with blue painters tape.
In reality, it is a great learning process, and it is not at all easy. This is my first printer, so I have a lot to learn about the extruder (which is the most critical part of a 3D printer). To get it to extrude smoothly is a huge battle, because I have no experience on where to look when things do not work (and it still does not work till today). But after a long struggle, and a lot of trial and error, I can say that I have a much better idea on the issues of 3D printer now, and how to solve them. I will talk about them in the next few days when I am still waiting for some parts to arrive in mail.
Here are a useful link about 3D printing.
On their website, they said that this is a "first general-purpose self-replicating manufacturing machine". I disagree with that statement. The machine only prints the plastic parts of the frame. It does not make any of the metal rods, the nuts, the bearing, let alone the electronics. That statement of "self-replicating" is a marketing gimmick. However, aside from that, there are tons of useful information on it, and a lot of smart people are contributing. If you need a place to learn about the in and outs of 3D printing, that is the best place to start.