I believe it starts for them on PBS in early May, and the DVDs would most likely be available for them shortly after that.  You're a kid--you know what it's like to want to peek at your Christmas present, even if it's just a corner of the package!  And especially if it were made by someone as super awesome as Steven Moffat and Mark Gatiss!  Even more so if you loved your last year's Christmas present made by the same people.  In fact, I think there was a reference to that concept in the Doctor Who Christmas special this year, which I recently purchased and watched on DVD.