randerson, the software is all loaded, v 0.75 is currently being shipped, working on options for tdi/audi at the moment. You can start with the wiki (don't need the assembly instructions). MPGuino - EcoModder
, You will need battery power, ground, vss and injector leads, then once installed you can go into the setup screen by pressing left and right buttons simultaneously (briefly) and use left and right buttons to navigate the values and middle button to change the digit at the cursor or select OK or XX (Cancel) in the setup screen while in the vehicle.
dri, if you should need an update for some reason, you can "chip swap" with an existing arduino. If you are really in a bind I can reflash it if you send it (the chip or the unit) back via S.A.S.E, for say, 6 months from receipt.
I would suggect check out the enclosure threads, I don't usually bother, but they can be made out of anything. The plug-in would require custom plugs for every conceivable vehicle, and the plugs would probably cost twice as much as the unit. It does come with a 3.5 floppy style power connector and crimp pins so you can unplug the guino easily once installed.