Jonathan,
Start here:
http://kmeleonbrowser.org/forum/read.php?f=3&i=1672&t=1669
for Hebrew, you'll use "he":
ser_pref("intl.accept_languages", "en-us, he");
Do you know what character set you need? If not, let me know as there were 5 options listed in Mozilla for Hebrew.
After you do that, you can read here:
http://kmeleonbrowser.org/forum/read.php?f=4&i=1256&t=1245
on how to set-up a macro for changing your encoding. Obviously, change yours from Chinese to Hebrew.
Andrew