If you're making a portable you probably need something to watch it on. (Unless you want to guess what's happening in the game, but I wouldn't advise that) Anyway, this forum is your "Hacking a pocket TV/screen" one-stop solution. Share your experiences and knowledge here.
If you do the led mod it wil little over half the power consumption.
It's worth it if you have access do the leds and you feel you won't break the screen while doing it.
But if you have a powerful battery 3000ma+ I would suggest just leaving it as is. It's brighter and crisper I'm told.