I think more information would help. When he says "What I mean is that the top screen isn't on the DS anymore. " I'm not sure if he means that the upper screen just doesn't work, or if he's misinterpreting the "top screen" as the upper half of the case, and that his hinge has broken.
Could you provide us with more information?
Does the top screen not display anything?
Does the ds boot up for a sec and then turn off?
Is it a DS phat, DS Lite, or DSi?
Is the top half of the DS broken, or is it the screen.
If you have some skills or someone with some skills you could probably fix it yourself cheaper than you could buy a used one.