Hey there! CorvidDude here. I'm glad you're interested in how the mod works, and probably how Sonic Adventure mods in general work. There's a huge amount of stuff in here, so let's break it down by folder.

root
|- part1.max : This is the 3d scene file for act1. This is where most of my edits are.
|- part2.max : This is the 3d scene file for act2. This is where most of my edits are.
|- part3.max : This is the 3d scene file for act3. This is where most of my edits are.
|
|-- export : Textures for each of the levels, as well as their nodetable exports are here.
|
|-- Levels : SALVL files and other SA Tools related files are in here, like the 2p path data, player start positions, etc.
|
|-- src : This is the source code used to compile the mod DLL. You will need Visual C++ to compile this.
|
|-- WV_Objects: These are the SAMDL and OBJ files for all of the object models ripped by Darkspines/ItsEasyActually.
	

I've released this in the hopes that more of you will learn how Sonic Adventure works, so you can continue the great tradition of using solid Sonic games as canvases for your creative endeavors. The only thing I ask is please, please do not mis-represent the source of this material. Sonic Team made the original level, myself, MainMemory, Catley, and Darkspines/ItsEasyActually made the restoration.

If you have any questions or are working on your own Sonic Adventure mod projects, head on over to http://forums.sonicretro.org/index.php?showforum=13
That's the place to go for this kind of thing. You can also stalk my youtube channel and G+ profiles listed below:

https://www.youtube.com/channel/UCXFoxv9pRE4xP-YLg8mhFrQ
https://plus.google.com/+CorvidDude
http://jcorvinus.itch.io/

Good luck!