Ok the navi car lcd is used bc it controls and sends signal to the subdisplay clock. I had to do some wiring to connect them by looking at the wiring manual. On the non-navi its just a clock and only needs power and illumination signal. No data from the stock non-navi control board LCD goes to that clock.

The radio info is usually displayed in the navi LCD (radio stations, xm stations, etc), and the top display on the navi is supposed to show some radio data like how many discs and track number. But it doesn't display any of that probably because I actually need the navi dvd unit as well.

It only displays clock, a little phone icon if you use HFL, and the AC temperatures and fan speed.The clock is set to 1:00 when you plug in the power, so i had to install it right at 1:00 which was no big deal.

As far as power, I think you jsut have to try it out bc that accessory lighter has a 15A fuse if i'm not mistaken. You can try switching to a 20A but its not recommended. I have a 4G wire to the trunk because of my bazooka so i just use that to power my laptop PSU which is rated at 90W.

If you wanna do a setup like mine, you will need to get the navi display and subdisplay which is NOT cheap if you buy them. I looked for them on ebay for couple months and got the LCD+ bezel with buttons for like $240 and the subdisplay + ac vents bezel for only $30 which was a bargain.

All you're doing is replacing the stock non-navi char LCD with the navi LCD and you have to connect some 9 wires from that to the subdisplay clock, replacing the existing non-navi clock which is interchangeable and nothing to cut or hack.
Hope that helps =)