Agreed, I wouldnt put anything on the top of your deck, but I believe your intending for most of it to be underneath?
The simplest thing would be to get a bunch of high brightness LEDs that you like and decide how many of them you want. From there you can decide what Wattage you need and you can get your batts. The best thing for your project would probly be a bunch of AA batts, 1.5 volts, wired in series. You can get these at your local radio shack along with the charger. From there you can decide what reisistance you need and your ready to start putting stuff together.
Also, it would be cool if you make your headlights out of hi-brightness white LEDs. the underglow, or whatever you had planned, could be other colors like red but these tend to be less bright than the white ones so pick your colors wisely.