Expounded Universe 306 – Mimban Number Five
You can’t get earlier Star Wars EU novels than this right here. Welcome to the “sequel in case the sequels didn’t happen” of Star Wars, where the force was still mysterious and Luke didn’t know who his sister was.
System Mastery 
The link here doesn’t seem to work, and if you check the page source there is an MP3, but it seems to be from episode 299… Episode 307 also doesn’t seem to be available on its page.