it can be fixed but you would be better off buying a new one,
the same thing happened to my digital camera, had it in my pocket, opened the car door but walked into the side of the door and screen cracked.
i then rang sony and they said the screens are �31+vat, the seal to secure the screen was �7+vat + courier price from their unit near heathrow to south wales, so can you imagine how much that would have been just for a 2.5in screen.
the camera was only worth �150 new.
sounds like it would be a similar case with your ds.
hope this helps.