The old battery didn't have much life left in it, but that was actually the smaller problem. The battery had gotten to the point where it had swollen so much that it was pushing up on the bottom of the track pad made clicking impossible. I had to enable some of the multi-touch features just to be able to click and drag and drop!
Very easy. Nothing was glued in this model, and the bottom screws are easy too remove. Too easy in fact, which is why I bought a screw set since 2/3s of my screws had fallen out and been lost. Good to have my bottom cover on securely and fresh loctite on the threads.
The walk-through calls out the spudger, but you really don't need it to bend the sticker over the left battery screw back.
Also, a great time to clean your fans if you haven't done so in a while.
P6 Pentalobe Screwdriver 2009 15" MacBook Pro Battery
MacBook Pro 15" Unibody (Mid 2009-Mid 2010) Replacement Battery
Macbook Pro Unibody Lower Case Screw Set