5. Where are all the textures?
Bundled up with all the other data for Heroes – in the data folder of your game’s install directory (likely C:\Program Files\Ubisoft\Heroes of Might and Magic V\data\, TotE has its own folder under Ubisoft and HoF has its own folder under HoMM5, dataa1). You need to get inside data.pak / dataa1.pak / whatever the TotE one’s called. Fortunately this is just a zip file, so you can open it with any program that reads the zip format. I recommend 7-zip.
Let’s pick the adventure-map Imp as a creature to retexture. You can find his DDS at: data.pak\_(Model)\Creatures\Inferno\Familiar_LOD-Familiar_LOD.(Texture).dds. (Yes, their names really are swapped round.) Navigate there now inside your zip program.