http://www.4colorrebellion.com/archives/2006/02/19/nes-ds-mod/
I wouldn't mind doing that to my DS if I was buying a DS Lite instead of trading for it.I took apart the entire DS, sanded off the paint and rubbed it down with brasso to give it a nice polished finish. Then I got a NES controller, carefully took off the face logo and touched up the odd bits with my girlfriends nail polish on the inside.
I didnt have to paint it as the DS case is naturally light grey. I cut some black vinyl then using an exacto knife, cut the details out of that.
I went for the style of the original DS with the black middle, but didnt quite get there.. still it looks pretty good. I cut the button holes in the top of the lid and stuck the NES buttons and Start and Select buttons through, but the Directional Pad I simply glued on with super glue.