How to Edit Main Menu and Load Screens?

Usually I can manage basic modding, but I'm unfamiliar with these two parts. Tips will be greatly appreciated.

1. I want to replace the load screen art with full screen images.
I'm stopped at the part where my full screen images are presented within the normal 'banner' shaped area access the middle, compressed.
What is the file that assigns the location of the load screen images and what is used to edit it?

2. I'd like to disable main menu movie backgrounds, and just use a 2D image for the main menu. What file controls the main menu movie and what do you use to edit it?

Thanks!