Mewtwo Strikes Back
It's not that hard actually. First of all load with AM the map where the scripts are executed. Then enable the Professional Header View option, go to the Header tab, and look for the Map Script Offset and copy it. Open XSE, load the ROM, paste the offset and enable the Level Script option (the button next to the decompile button). Finally, decompile. As usual with text editing you can't change the text so it's longer or you will overwrite data. That's when you need to repoint.