As far as the DS is concerned there are plenty of people who can tile edit (you say you are not an artist which is fine but being able to pull graphics from a game to give to an artist is a useful ability), create tables and do little hacks based on the file system used by DS roms or the filesystems of the file contained within the main file system. These however are the bread and butter of hacking so knowing this is a must.
Most lacking is those capable of low level assembly, specifically reverse engineering of file formats, compression and encryption using an emulator (not helped by a general lack of tools for the DS).
After this is general file format reverse engineering; too often do I see people get tied to tools (narctool and pokemon provided a good example) and when something is slightly different (reverse engineering is not flawless after all) the headless chicken approach appears.
As far as translation teams assuming they get a translator or two then it is either the grunt work of table finding and text dumping by way of there being lots of it or help finding the odd things buried deep within roms (basic game text is usually fairly obvious but little strings in menus and such that finish off the translation can be buried deep within the binary or graphics).
As for Japanese learning the basics (what are hiragana, katakana and kanji), not an especially large amount of translation is based on Japanese language manipulation (for an English language hack I will look at distribution as space is most the likely, relative searching is useful.....)