So easy, replaced the battery with my girls!
The trackpad would no longer work because the battery had bloated and was causing pressure against the frame.
The repair guide was easy to follow. We didn't end up using the solvent to dissolve the sticky tape. Instead, I carefully pried the batteries with my fingers. I also left the tap eon the back of the new battery. I didn't want them to stick to the case again. The battery fits in the casing tightly so there is no need to fasten them with the tape adhesive.
The guide on the site makes it look like you need to follow steps 1-30 before getting to the battery. Even the pictures show the battery being removed from an empty casing. This could be confusing to someone who didn't understand from the guide this is unnecessary.