The shipper is reusing tracking numbers from last October, so you can ignore messages from then.
For Dropbox, just open the app on the tablet (it's in the Galaxy Plus group in the app drawer) and sign up. You'll get the standard 2GB but you'll get an e-mail a few minutes later titled "Claim your 48 GB of free Dropbox space!" Follow the link from it.
You have to complete at least 5 of the activities listed, but two are given-- you already have it on a mobile device, and you already have files in it (you get a welcome to Dropbox pdf). I flipped through the getting started guide, added Dropbox to my desktop, and "shared" a new folder with an alternate e-mail address of mine. I got the total of 50GB right after that.