My phone still works great, but the battery was so old that it just wouldn't hold a decent charge anymore. The phone was not designed for the battery to be user-replaceable.
IFixIt assured me of how to go about it. I researched online and finally found a reputable replacement battery supplier, and I also bought a tool kit from IFixIt for use in getting inside the case of my phone.
It went exactly as described. The guide answered all my questions before I encountered them. I took the old battery out, put the new one it, and BINGO! Glory & Trumpets and all of my dreams have come true! I couldn't be happier with the process, because it went without a hitch and I've never pried open a cellphone case in my life. Thanks!