Hello! Using my game for visual content for tutorial? It's an honor for me!
You can edit your RGM game's content in /rgmsys folder. Just find a file and write a format in filename. For example: menu1.bmp. Then you can edit the file and when you're finished - delete the format. This method adds you some undocumented abilities. For example - you can resize bitmaps to other resolutions. My main menu's realization is just resized bitmaps. I gave an offset for menu button and that's why it moved to the right side of the game window.
That's the trick. Good luck and can I ask you for link for your tutorial when it will be finished? ))