It's all been pretty much covered, but I'd just like to add:
You should have just not bought it when it came in. It's not like your FLGS had to bend over backwards and call in favours to bring the Beginner Game to you - they probably got a crate of 'em. It's not hard to say, "oops, sorry guys, this product isn't what I thought it was going to be, and I don't want it anymore. Sorry about that." The store employees surely wouldn't have batted an eye, as they could easily sell the copy to somebody else.
I think you, as you say, 'geeked out', and just had to get that box home and tear it open, even though you knew it wasn't what you wanted. And when you did, you felt foolish because it (wait for it…) wasn't what you wanted. These are just my impressions, of course - I don't know you or your thoughts.
Anyway, it's yours now… maybe there's a little junior roleplayer in your life somewhere who could have fun with the set?