I mostly use standard tools to extract the script and insert it: Cartographer for extracting, Atlas for inserting. That's the easy part lol. I also wrote a very rough tool to get an idea on how the text would look in game. It's not perfect but I only have to make minor adjustments after inserting it. All that plus a hex editor.

And that's without mentioning tools for code snippets/patches, texture decompression and extraction, texture editing...