I recently completed this guide and everything went very smoothly. I skipped many of the steps leading up to the adhesive removal, and only found it necessary to pull up the left and right speakers. My adhesive remover had evaporated, so I just used some nail polish (100% acetone) and leverage to get the battery cells to come off the case. Be aware that once you stick the batteries in, they will be very difficult to pull back off. I put mine in slightly crooked, but everything powered up fine and my macbook's battery is good as new. My only real struggle was that since I put my batteries in a bit crooked, the case back wouldn't attach flush to the body, so I had to go back in and wiggle the small tubes surrounding the main cell so they would be seated properly.
Thanks for the guide!