Like all things seem to, my mba's battery had bit the dirt. In fact, the battery had been giving me "Service Battery Now" messages for about a year before I did anything for it. I'm glad that I did; people speaking in the third person kinda creep me out!
-buy a replacement battery
-buy necessary tools for replacement
-tell you all about it
Getting the whole bit set was definitely overkill, but now I'm prepared for most any type of computer repair. Phillips' heads, pentalobes, hex - everything!
As for the laptop itself, the rear panel was simple enough to remove and the battery was only connected to the system by a single cable. Making things even easier was a nice little pull-tab on the connector that kept me from needing to use any pliers (I have big hands) that would put undue strain on the components. The new battery fell right into place! Some 12 screws (or so) later, I was back in business. My battery life has increased from ~2Hr30min @ max charge to a total battery life closer to 7Hr. Whoo!
Let's just say that GEICO would have something so say about this procedure.
Make sure that you have a clean surface to work on and have a means by which you can keep track of your hardware. The screws are tiny!
Of note: The screws enter the back panel at funny angles to allow for the nice tapers that you see all around the laptop. Keep that in mind when reattaching the panel.
(Good luck! You won't need it.)