Quick messy guid.
1. Take out the battery.
2. Pop off the rubber pads on the bottom side of the DS Lite.
3. Take out the screws in each corner, and also that were under the rubber pads, and also the center screws located in each slot. Should be one screw you didn't touch in the battery bay, leave it alone for now.
4. Pull the case of the DS Lite at the GBA slot very lightly away from the body, this is a locking mechanism, and lift just a little bit upwards.
5. Now pull the entire bottom shell straight up slowly and carefully, you don't want to break any power or volume control pins.
6. There are two screws (I beleive can't remember from my previous adventures diving in) that hold the DS Lite mobo down, take those off.
7. On the underside are the ribbon connectors, for the big ones flip the black flap up (not sure if this is in the DS Lite, for the DS it's in there). If there's no black flap, take a small slotted screw driver and push the brown thing under the ribbon flap outward. Then pull the ribbons out.
8. Take the mobo out.
9. To open the top take out the rubber pads on the inside of the top screen.
10. Take the screws out.
11. Once they're out, slide the outter shell away from the DS Lite hinge.
12. Then slide to the right I beleive if you were looking at the DS Lite from the outside.
13. Pull thhe shell off.
14. Take off the LED housing on the bottom half of the shell by unscrewing two screws.
15. slip the ribbon for the top screen through the bottom shell using that slit they provide.
16. Your DS Lite should be pretty much dismantled at this point, lol.
If you don't have a triwing screw driver, I can suggest using a Craftsman 3/64 inch slotted screw driver, or a 1.2 mm slotted screw driver. They work just as well unless you get some cheap one that breaks all the time.... Anyways, don't forget to ground yourself before you touch that mobo, might short circuit it if you dont, then you'd brick your DS Lite.