I've heard that with the right equipment (which I presume is this M3 thing, you can get linux on your DS. Does anyone know how to do this?
The DSLinux Wiki suggests using a slot-2 device for best compatibility - either a SuperCard (non-rumble) or an M3 Perfect. I suggest reading all of the articles under " For DSLinux Users".
I have an M3 Simply, which is Slot 1; and it doesn't seem to run for me... I don't think you can do it on slot 1; but I may be wrong.
Yes, you can, especially since a DLDI version was released very recently. Get the 'dslinux-dldi' builde from the DSLinux Download Page and patch the *nds using these instructions.