I think I set it to keep the images in the library not referenced but the drive did contain many pictures before I started using Aperture so i need to bring them into the library.
How large is your library now, and how much space can you afford for your Aperture library on your internal drive?
Or do you have a second exernal drive, that you could format MacOS Extended (journaled) to be able to temporarily host your Aperture library?
Do you need the "Tuxera NTFS" formatting on your external drive to share image files with other systems, or would it be an option to reformat that drive?
If you are more comfortable with a managed ibrary, by all means keep the library managed. Only it needs to be on a drive formtated MacOS X Extended (Journaled). It could be your inernal drive, if you have enough space or a locally connected external drive. Connect it to the fastest port you have; Firewire, or Thnderbolt, a fast USB port.
Move the library there, then import the images, that you now have in separate folders on your externa drive. To prevent Aperture from importing duplicates, enable the option "Do not import Duplicates" in the import panel. If you are lucky, Aperture will recognize many of the duplicates. if you have not changed the filenames.
I have to sign off for the next couple of hours, but will look in later.
Regards
Léonie