Yes, the method explained in the webpage that apoqueo pointed is the same as I suggested.
Time ago I tried to change the full Monkey Island 2, but I hadn't enough spare time. Even so, I learned some tricks that you can use when modifying datafiles:
Making .TBL files
Hexpose (that hex editor) can make a sort of "translation table" that maps hex codes to more useable symbols. Open a datafile in Hexpose, and search for an option called "Save .TBL" in the menus: it'll create a basic map file. Then search for conversations with special codes like the spanish "ń", or other like "ˇ", "á", "é" and so on. Add them to the .TBL file (the format of the file is very easy). Now reopen the datafile with Hexpose: the special codes appear translated in the text window! And you can type that characters in the text window and thy will be translated to the appropiate hex code when saving the file! Note that you can map an hex value to more than one character.
Scumm uses several special hex codes into strings: thay are used to insert line breaks, delays... I don't remeber them now, but they are easy to find as they appear in the middle of text strings: just try to figure yourself what that code does by playing the game. You can map them into the .TBL file, too. Note that are two and one-byte codes. These opcodes can be inserted anywhere into a text string.
There are codes for the beggining and the end of strings. Add the codes for that codes into the .TBL in order to "see" lines better. I used ">>>" for begginings and "<<<" for endings.
Hope these tricks will be useful to you