As far as I know, modding can only be done on the PC. This is because of the essential difference between how the information is stored. On the PS3, the information is burnt onto a disk, the information transferred to the unit when it`s turned on. Inside the computer, the information is written on RAM memory (Random Access Memory). This means the information can be changed. This is why modders are always told to make a backup of the orignal before installing a mod... you are literally erasing the old information with the new information of the mod.