Well, BN.com has a pretty good price on the Core Rulebook pre-order, so that might be a good deal to get in on. 35% off is nice. Note also that the book is not coming until July.
The Beginner's Game is out and can be obtained from your Friendly Local Gaming Store or wherever else you buy those products. It's an excellent value at list price, since you get a $15-value dice set plus a map, tokens, adventure, cool-looking folios for players, and not to mention the freebies on the game's support page here on FFG's site—two more character folios and another extensive adventure.
How you transition from the Beginner Game to the Core Game (This is totally unofficial and is only my opinion, so take it as you will):
The pre-generated characters should be able to lift right out and be assigned an appropriate base Specialization. They'll have a few free talents from the Beginner's Game, but this is a game where you don't have to "show your math work" and be able to reverse-engineer your PC to level 1. So, for playing in the Beginner's Game and as an incentive to keep your character, here's some unattached talents. Also, you'll have to decide on a specific Knowledge skill a specific Piloting skill if you want to convert those characters over to the Core Rules.
And besides the pre-gen characters, really all the stuff you get from the Beginner Game can be used in the Core Rules. Maps, tokens, adventures & adventure seeds, dice.
The Core Rules will provide a MUCH more in-depth experience; such as extended Talent Trees and actual specializations; the sweet, sweet Obligation mechanic; more species; critical hit & critical injury tables (I love these, and miss them in the Beginner Game); and all-around more expansive rules on personal- & starship-scale combat to enrich your games (not, as one might think, to bog them down).
Oh, and there's a chapter on the Force
Not to mention more GM aides in the form of charts and tables, another whole adventure, and a crap ton of (what I know will be) beautiful artwork.