Female pilots and the like

>When did we first learn that Han was Corellian?, When was "Sith" first mentioned?<

All of this information was presented in the A New Hope novel, and other adaptions like the comics and the radio drama. It had all been in the script too--it was just cut from the film.

>That Boba Fett was a Mandalorian?<

The Empire Strikes Back novel stated that he wore Mandalorian armor and the Marvel comic series actually stated that he was Mandalorian, but a slew of subsequent backstories conflicted with this information. It wasn't until Attack of the Clones tie-ins like the Jango Fett one-shot and Open Seasons came out that we learned all about Boba Fett's real connection to the Mandalorians.

>That Princess Leia was adopted by Bail Organa?<

This was explicitly stated in the Return of the Jedi novel. (Again, more information cut from the film.)

TC