the script is the quite blatantly labelled scriptxxx_LZ.bin (it could be event, i forget) or whatever. as its name suggests it's lz compressed.
the way the text is written is through textbox initializations, rather than counting string length, so theoretically, you sohuld be able shove in as many textboxes as you want, but i'm not sure. when i hacked this game, i didn't know that you had to check if more space was available or whatever.