wow no need to yell buddy Usually replacing something yourself is a hell of a lot cheaper than having a shop repair. Also some people like to replace their cases/shells with different 3rd party products, or make modifications themselves.
Like Anandjones said there is a great video showing you exactly what to do but its not easy and you need a speacial screwdriver. x
It's quite difficult so if your not very technical or you've never dismantled so much as joy pad then i wouldn't recommend it. As already stated it also requires a special screw driver which you have to purchase. What isn't stated here is that the DS can be bricked if the cable connecting the top half of the DS to the bottom half is broken. The cable is one of those flat, flimsy cables which snap like wafers and apparently cannot be replaced. If the worst came to worst you could replace the whole top half by buying a parts DS from Ebay but that would cost yet more money.
Yeah, first you need a tri wing screwdriver... make sure when you open it that you keep the screens facing down. that way, after the cover comes off, the buttons wont fall anywhere
The guide on GBAtemp is pretty good and walks you through step by step, triwings are pretty cheap, I picked up a whole set from local electronics store for $5
