The battery life in my iPhone 5s had deteriorated until the run time was less that an hour. Being technologically challenged and on the downhill side of life, I wasn't about to invest in the latest, greatest phone. !&&*, I don't know or use half the capacity of this phone.
Living in a rural community has challenges when it comes to purchasing repair parts for almost any household item, much less cell phone parts, but iFixit was easy to use. I got the right battery, followed the instructions (removing the battery is more difficult than described) and I'm back to communication with the world.
Don't be afraid to do it yourself. The repair guide was spot on. Have patience and it'll help to have a magnifying glass!