My wife was experiencing poor battery performance. Apple refused to help because the product was out of their service window (over 5 years). I had to turn elsewhere to solve.
Easy peasy. My recommendation to iFixIt would be to detail putting the battery back into the case. Even if the line simply reads "Once battery is removed, reverse the steps above to connect new batter."
That's primarily due to the fact that the battery I received had a plastic film that covered each lithium battery pack. Since the battery i removed did NOT have the plastic film, i wasn't 100% sure if i should try to remove or not.
It can feel pretty intimidating to take on a repair like this. But go for it! The effort is well worth it.