With your new mod structure setup you can now start creating your mod. Now, just because you started with one mod type doesn't limit you to just modifying the couple of assets you'll find in your mod's Content Folder. You can modify any number of assets from Robo Recall and have them exist in one mod.
Just remember, that any new assets you import need to go into your mod's Content Folder. If you put them elsewhere, they will fail to package!