I bought the "OpenEVSE 30A Charge Station Combo - Built - No LCD", which is pretty much all the parts, except the J1772 cable, an enclosure and a few miscellaneous connectors. It really was not difficult at all, as long as you are comfortable with this sort of thing. If you were able to run your own wire and install the outlet, you should not have any difficulty with this. If you are more technically proficient than me, you could buy the unassembled kit for a bit less money. I was kind of afraid of the soldering, fearing I would put something in the wrong spot or fry an IC.
It is called 30 amp, but actually charges at 24 amp. I'm finding the whole current thing a bit imprecise, including the Nissan 6.6 charger that never really gets to 6.6 KW.
If you do decide to build your EVSE, feel free to Pm me, or post on this thread, and I'll give you all my insights as a first timer, relative electronic neophyte.