Here's some basic information about the DS that you need to know before hacking:
First: The DS is little-endian, like Intel processors. This means that the Least Significant Byte is first. Hence, if you're programming C code on the Intel, you can read directly into the structs I provide. PowerPC programs will need to have endian-ness flipped when reading and writing.
All DS ROMs are in .NDS format. This can be un/packed with dslazy. I may borrow a description of the format later.
The DS uses both an ARM7 and ARM9 processor.
.NARC files are very important. For now, use narctool-0.1-p. I will try documenting this a little clearer, but the narc.h file in the src directory provided should help.