It's more complicated. There's a ribbon cable that runs through one of the hinges, and you have to disconnect it from the motherboard in the bottom in order to feed it through.
Three pieces of advice (I've done this twice now as my hinge broke this weekend on my shock case - 2 weeks old.
):
1. Make a sheet of duct tape with sticky side up (several sheets overlapping) a bit larger than your ds. Use a sharpie and make an outline of your DS on the sticky side. I drew in the buttons and battery cover on mine. Every time you take out a screw, put it head-down on the duct tape sheet in the same location it came from on your DS. You'll never confuse the screws this way.
2. To keep the switches in place as you put the bottom back together, move them to the right place (down for the power, and I put the volume one in the middle) and put a piece of tape over the OUTSIDE of the switches. This will stick to the switches enough to keep them in place.
3. EXPERIMENTAL: To avoid the deadly hinge breakage, super-glue the "positioner" doohickey into the hinge. The hinges break because when you open the cover, you're pretty much pulling the back of the hinge off, and the front of the hinge takes all of the pressure...snap! If you glue all sides, the stress is spread over all sides of the hinge and it's waaaay stronger. WARNING! This does mean that you'll have to break your upper shell to get the doohickey out, and in fact it may not be possible to get it out cleanly. I would love to know if you can get a replacement. I know there are shells that include this ALL of the parts, and I guess I'll have to go that way if this case breaks, too. Also, I only did this today on my (completely) broken hinge. So far so good, though, and I think it should be fine.
So be warned.
One good is that you DON'T need to disassemble the top half to do this.