a little confused you are.
hacks no, there are none, what you hear about, are mods. Mods are very Legal, and are even created by using the tool set that comes with the game (PC). Just google, Morrowind Mods, and you shall see. The mods themselves will be a .esp file, but may also have textures, icons, or models that are packaged with the file. You'll need all of them, just place them in cache directory(x,y,z) along side Morrowind.esm. Be sure to keep the directory structure the same as came with the mod. That's the simple answer, there are more complex ways of modding, to keep the mods permenantly or resolve dialogue problems, but you'll need to read these forums a little bit better to find that answer.