@fana10824 since iFixit does not yet have a specific guide for this, use something like [https://www.youtube.com/watch?v=50wU6y3y7J4|this video]. Replacement batteries are readily available at many online stores. Just pick one in your geographical area since some sellers do not ship batteries.
While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.
Repair is War on Entropy!