I have been reading some material about E.L. James and her Fifty Shades of Grey series. It seems she originally wrote this novel as fan-fiction, and how she decided later in life to make it an original piece of work. Does anyone know what she changed from her fan-fiction to original work? Did she just change the character names and remove direct references from the Twilight Saga for which that fan-fiction was based? I have a couple of fan-fiction screenplays that I would love to re-create to make them original. How can I achieve this that won't be a red-flag with respect to copyright infringement? I'm actually working on a project now and I changed all the character names to something more original, and changed the entire world/background to something that I made up. I also created original scenes for that fan-fiction and am now bringing it over to the original work. Is this okay? Am I going far enough in making sure I'm writing something wholly original?
It's certainly been done before, but without knowing the details, it's hard to say whether your changes are big enough.
Find some beta readers who don't know your connection to the fandom and ask them to read your stories. If you get feedback that the story/characters etc. remind them of the original story, you might need to make further changes.