open the .py files with IDLE, and use ctrl + f to find what you are looking for. Other than that, i really dont know how to help you. Though a lot of the menu stuff can be found in game_menus.py. I know literally nothing about scripting so anything other than this i cannot help you
EDIT:
Press ctrl + f and paste this into the box
("begin_adventuring",[],"Become an adventurer and ride to your destiny.",[
From below there, you can modify what the player will get if they choose so and so background thing. The game organises it into the series of choices you make. By the way, the lines in red with the ## at the start are disabled lines, from older versions of m&b i think