Okay...after a bit of clicking around I found most of what I was looking for under the Campaign option. Didn't even think to look there. I was under the impression it would present itself more easily.
Your answer, however, doesn't tell me how to find the "Precursor Worlds DLC", "Mega Events DLC" unless those are hidden in one of these scenarios:

Also, the "Builder's Kit DLC". I'm not 100% sure but are these just more items that were implanted into my current ship designer or is this something available outside of the game or another option in the game?
If they simply implemented more items into my current ship designer, how do I access the letters/numbers and the new parts? I'd like to build a ship from scratch but when I fire it up inside of one of my games, I still don't know where these new parts are at.
And lastly...the soundtrack am I to assume it's just the MP3's I'm finding in the /MUSIC sub-folder in my STEAMAPPS\COMMON\GALACTIC CIVILIZATION III sub-folder?
Man...the devs AND marketing don't make finding this stuff easy.
Anyone else care to elaborate to help a fellow player out? Thanks!