My MacBook was showing the 'Service Battery' alert. I asked for a quote from an Apple repair store who were going to charge almost $300 for a 10 minute job.
Repair was simple. No worries at all and all of the tools worked perfectly.
Replacing the battery is incredibly easy. If you're able to, never settle for the heavily overpriced repair stores. There are plenty of sources online to buy replacement batteries including on ifixit but ifixit also have all the necessary tools to carry out the repair.
Metal Spudger Set
P6 Pentalobe Screwdriver 2009 15" MacBook Pro Battery
Anti-Static Wrist Strap