How to setup a mod
Mod-sdk works in a way that overrides original files within the game by rerouting reads to a different folder or a 7z archive. For example, if you want to replace Jill's default outfit model, in your mod folder just create a file with path DATA\PLD\PL00.PLD and the game will load that instead of the original file.
Create a mod folder by calling it something like mod_xxx, where xxx is your custom identifier. Populate this folder with a manifest to make the game detect the mod. Now you can start adding files to the mod as if you're editing the main game. Check this page to see all the other files supported by mod-sdk for quick edits of game data. If you want to get fancy and give your mod a custom title bar icon, add icon.png to the main folder of the mod (size and color depth don't matter). More information on how Developer mode works can be found here.
To release a mod, take the contents of your mod_xxx folder (not the folder itself, just what's inside it) created in Developer mode and compress everything to a 7z archive of the same name. When doing this make sure you're using s=off in the parameters, so that it turns off solid archives (they tend to load very slowly by design). Use the following settings if you're not sure what to do the first times:
