Just downloaded it to take a look. The font's located at 0x00093873
, 8 by 16 pixels, easily viewable in 2BPP mode.
It goes 0 - 9, A - Z, Katakana, Hiragana, punctuation/symbols/dialogue border, then finally "accented" Katakana and Hiragana.
I'll try to figure out the encoding when I get a minute, but it seems like it could all fit in 255 characters.Edit:
Ah, if you've been given the scripts already then you must know the encoding.
Regarding image editing, what graphics do you need changed? I saw a bunch of uncompressed images while I glanced through the ROM, so at the very least I rip them and give you the hex locations to reinsert them once edited.