I have opened up at least a couple of dozen old and new 3Ds's. I thought I should add my experience with those tiny ass cheap screws. if your screwdriver doesn't seem to fit, and it feels like it's wanting to strip out the slots on the screw face, stop. find another screwdriver that fits better. If it doesn't want to fit right, try the others while being careful not to strip them. if at that point you can get at least one out without damaging the others, take that one you got out and take it to whatever type of store that is around you (Fry's, radio shack, harbor freight tools. etc) and find a screw driver that fits.
A lot of the electronics that people bring to me to be repaired have signs of someone else trying to "fix" it themselves. The client will swear up and down that no one has ever tried to open whatever device it is, but stuff doesn't get shipped from the manufacture like that. Most of the time the screw faces are stripped. I don't try to argue with them. I just tell them if it's (let's say it's a device with a stripped screw face) stripped and I can't get it out, I will have to charge them $10 per screw to cut a new slot in it.
Moral of the story? Any time you are in a situation where you have to unfasten very small screws like that, go slow. if it doesn't want to seat properly, get another screw driver that does. When a manufacturer tries to go cheap on such small fasteners, the metal is usually not strong enough to withstand the shear force of a screw driver that doesn't fit properly.
