My note above should say 1/31/13. Here's what it says in the fine print when I try to order:
"Save 50% On AppleCare Protection Plan for Mac mini
Limit 1 items below per bundle • Expires: 01/31/2013"
I ordered my mini a few days ago - it's still in transit, ordered 12/20 and I'll have it 1/3 (slow shipping to Washington, huh). When I ordered it, the date was 12/31/12 - but now it reads 1/31/13, so I think they've just extended the low-cost Applecare another month - maybe they'll do it again next month. I guess we'll know tomorrow.
As for getting it into your cart, when adding the free software, look a bit lower and choose the Computer Accessories tab and choose Apple care for $54. If you just add the mini to your cart, exit the next screen, then look at the cart it'll show applecare available - if you pick it then it'll add and be $104!
EDIT: BHPhoto has a NO RETURN policy if the computer is opened. I'd expect them to take back a buggered up shipment but there's no 14-day return window as if you bought it from Apple directly.