Great, I will be more than happy to assist you.I'm ready to start building this - can the code.google.com site be updated with parts lists? I have some experience with the Arduino, so that should not be a problem, but would need more details on which LCD you're using and which power supply.
I'll place the order for the Nano and get it loadable so when the next firmware rev is ready, I can blast it right in there
Nano is a great choice.
Regarding LCD - I got one that comes with I2C adapter on it. Makes life really easy. A regular LCD is going to be a problem as it uses many ports, and you don't have these ports available.
I2C is great because with 2 wires you get a bus that all I2C devices can share.
Look in ebay for:
"Serial IIC/I2C/TWI 1602 162 16X2 Character LCD Module Display For 5v Arduino"
For $8.59 it seems like a great deal.
Interesting thing about the LCD modules of this form factor, is that their holes match exactly the holes of the enclosure I used - HM1038-ND
You don't have to use that enclosure, but it should fit all the components nicely. If you look at the google code video and photos you can see the enclosure's dimension.
Power - I drew the power for the LCD from Arduino 5V port. I converted the 12V (~11V-15V) from the motorcycle's battery into a stable 9V using LM2940 and some related components as seen here
Then I fed the stable 9V into the Arduino's VIN port.
The Bill Of Materials I have for V1 is not 100% right for you since in V2 you don't need the following:
1. Arduino shield. Instead buy a cheap Radio shack thru hole PCB and headers and put all the components there (i.e. make it a 'nano shield'). I checked and the nano easily fits the 0.1'' PCB.
2. Enclosure for Arduino
3. Ethernet Dual Port
4. DS1631 Temperature Sensor
5. You probably don't need the 14V Zener - I was a bit paranoid
EDIT: I loaded the same firmware to the Nano. No issues. I didn't connect any peripherals, but the firmware works as designed, and I communicated with it using the serial port - it has kind of a console command line interface for diagnostics. No need to wait - just use it.