I recently purchased a crystal clear DS lite replacement shell from dealextreme.com for a little over $16.00. You can buy replacement shells from many different places, such as ebay, but dealextreme had the best price and free shipping.
I didn't see an Instructable about how to replace the DS shell so I decided I'd write one up. It's a pretty complicated process and took me about 3 hours to complete, so I figured that a lot of pictures and descriptions of the process would help others. I labeled each section to make it easier to find a specific part of the process.
You WILL need a tri-wing screwdriver for the replacement so either get one off of ebay or if you place an order with dealextreme.com, add one to your order. You will also need a small phillip's head screwdriver, a flathead screwdriver, an exacto knife, a soldering iron, some de-soldering braid or solder sucker, and possibly some needle nose pliers.
When taking your DS apart, pay attention to how everything fits. Don't just rip it apart, take notes if you need to. It really helps in the end. When you put the DS back together, the hole will probably not be threaded so it may take some force to get them in there.
Step 1: Disassembly: Part 1
Taking the Back Cover Off
The first step is to unscrew the battery cover and remove the rechargeable battery. Also, make sure to take out your GBA cartridge, stylus, and DS cartridge if they are in the DS.
Next, you will use your tri-wing screwdriver and a small phillip's head screwdriver to remove all of the screws. on the back. The blue squares are screws that are covered by little square rubber feet. You can use a small flathead screwdriver or an exacto knife to remove the covers so you can get to the screws. Also, don't forget the little black screw in the DS cartridge slot.
After all of the screws are out, you can SLOWLY pull off the back cover. You want to be careful to hold the shoulder buttons when you take this cover off because they are spring loaded and will go flying if you're not careful. My replacement shell came with some extra hardware such as screws and pins but it did not come with the springs for the shoulder buttons. Pay attention to how the shoulder buttons are placed!!!