You translate DS games just like every other console, becuase I got bored one day I wrote up a guide to it (PDF document):
http://www.4shared.com/file/3636881/1f5f088d It is not quite finished yet but it should give a nice overview.
As for final fantasy3 the game uses uncompressed shift_JIS character encoding with simple pointers (flip the bytes to get the offset needed for the file required) and so was a fairly simple task.
I have not taken a look at Chou Shoujuu Mecha MG but it may be more difficult, especially if compression is involved.