How much do the live-action Nana films cover?
The live action goes up to episode 19 of the anime series, which in turn is shorter than the manga (only goes up to the 12th volume out of 21).

There's a lot of plot and relationship changes that happen in the future chapters, rather than spoil them here you should read to find out :D

Unfortunately, the manga does not have a conclusion just yet as it was put on hiatus in June 2009 when Yazawa became ill. So just be aware that there is a lot of loose ends in the current final chapters