There will be little or no impact if this is performed before the player has entered the Isles at all so it is preferable to get rid of vampirism as soon as possible if the Isles have not been entered yet.
If Shivering Isles quests are active, they may disappear or bugs may occur. Keep your pre-workaround savegame just in case.
Right off of the bat, I can see that you are in a bad spot. The method for fixing one bug, with the PS3 GotY Disc, can cause other bugs in SI. You are just one of the Unfortunate ones to have encountered this.
With the PS3, you have little choice but to go back to a previous save:
1) Preferablely, if you could go back to a save before you started SI, and then do the Cure work-around.
2) Before you did the work-around for the Vampire Cure, and just play as a Vampire, until you Complete SI.
3) Start a new game.
Even with a PC version, one would be hard pressed to find a Fix for the situation you are in.