If I remember correctly (I seem to have read all this somewhere but I can't remember where) you can't add new functions to existing scripts because they are "baked" into the save.

Does this mean I have to make a new script called Updatexx everytime I want to update or do I move everything into a new script and just leave properties behind?

Whats the best way to do this?

Thanks

This should answer your questions. You can add new function to your script with no worry.

http://www.creationkit.com/Save_File_Notes_%28Papyrus%29