just to ask the people who can convert stuff here, would it be possible for someone to rip cars from Nintendo DS games? (namely Mario Kart, cuz some of those karts in revolt would be cool, and some of the tracks are killer)

there might be some .nds extractor to extract all objects from a DS ROM image. Then again, it is highly illegal.. Without Nintendo's permission. As the tracks and carts are still under copyright.

Well, GT2 cars are as well.

Hmm, even if you got the files extracted from the image, what would you do with them then? They are probably in some unsupported proprietary format that no one has cracked except the devs themselves.