Update - There is no way to extract the Savegame.sav from a PS3 save file. In short it doesn't work for the PS3, sorry.
Program In Action
How to use
1 - You will need either Modio or Horizon downloaded and open.
2 - Drag your gamesave into Horizon/Modio
3 - Click on the contents tab
4 - Extract the SaveGame.sav from the save file
5 - Open it up in the editor
6 - Make changes then hit save (Rename it to SaveGame in a different location than the original)
7 - Replace(not inject new file) SaveGame.sav with the modded one.
8 - Rehash and Resign
Click Here To download the tool
You use this Editor at you OWN RISK and remember to make a backup beforehand.