Board Thread:Skyrim/@comment-12758041-20130720014612/@comment-6881629-20130721171316

Game progress is in the Save Data Utility the file will have your characters name in the info. Lots of people have done this with no problem but they had the individual DLC not Legendary Edition.

Its a long shot if this will fix the quest if your really worried don't do it and try again for Lost to the Age in another playthough.