Assembly is straightforward but takes a while. Comes with all the tools you need. Everything is metric. I recommend labeling the screw packets before starting so you know which size is which.
I ended up tightening the drive belts after initial assembly, which is tough to do. I used vise grips to help.
I also added a couple washers (of my own) to the pen mechanism to reduce slop. On either side of the arm that raises / lowers the pen.
There are two software packages, one is Windows only (Benbox) and the other is cross-platform (mDraw). I've only used mDraw. Each ships with its own firmware I think.
Their software is crappy but good enough as a starting point. It's easy to roll your own software in any language that can connect to the serial port. Baud rate is 115200.