Like most bios systems in motherboards, from my experience, the worst that can happen when the battery dies is that you lose your clock.
I would think the information on your box ID for subscriptions will be embedded information on the board itself. I wasn't sure what you we're talking about before. When you said ID, it slipped my mind for a moment or so and I realized you have an addressable box.
Get a new battery from walmart and you should be ok. That is, if it's a common lithium battery.