This was my first computer-kit, and it was fairly easy to assemble. There aren't that many components and everything was included in the box.
The seller shipped the order almost immediately, and the package contained everything needed. The only thing that griped me a bit was that ESD-bag for the serial-module was cut open and the module had escaped during shipping and were floating around freely in the box. The other two modules were in sealed ESD-bags. Sockets and IC's were attached to foam to keep them from rattling around too much, but unfortunately a few had detached anyway during shipping, resulting in some bent pins. Nothing that could not easily be fixed though.
There weren't that many instructions included in the package itself, but most things were easy to figure out with the BOM and the well marked board. There is information on the github-wiki that is linked from the page here too. There is also a few youtube-videos to get you started. They don't show full assembly, but some handy tips to get you there. The videos also take a look at how booting works and how to reset to the boot-menu once you have made an OS-selection.
I used a multi-meter to test the resistors (since I am not that keen on the color-coding and math involved in that yet). It also helps having some tape handy to keep some of the components in place while soldering (mainly the sockets and other short-legged things), and perhaps some kind of holder or helper for the board itself. Other than that, a soldering station, and some thin solder should do the trick.
When assembly is done, everything is included to get you started. A USB-cable, and an SD-card preloaded with some OS:es and basic interpreters and the like. CP/M is probably the most usable out of the box for users that have some familiarity with DOS and similar systems.
My overall experience with this kit is very positive. It was fun to build and poke around with after assembly. The next step for me is probably to find some box to build this into, and perhaps add a terminal-module so that it is a bit more self-contained.