I've had this phone for almost 4 years now and it's still fantastic, only the battery is dying and needs a replacement.
I've done part replacements for phones before so I have a bit of experience with this sort of thing.
However, looking at the guides on YouTube and reading other peoples experiences, this looks like a VERY hard task since the phone is glued together and the battery is glued to the back of the screen for some reason.
I'm thinking of taking it to a phone repair shop and getting them to do it since I wouldn't have to worry about messing up my phone and then having to buy a new phone.
If anyone has some advice/insight on what to do please let me know. Also if you can recommend a shop to take it to that would be fab as well.
Cheers.
If I had to rank your options from best to worst:
I probably don't need to explain why having a mobile repair shop fix your phone is the worst idea — you're spending maybe $80~100 dollars extending the life of an already old phone and using money that could go towards a brand new unit.
I watched the repair vid and would rank that as probably a 6.5/10 in terms of difficulty, but much harder if you do not have the tools to deal with glue (e.g heat gun)
you might need some isopropyl alcohol to dissolve some of it so you can pry the battery out of the case without damaging the rest of the parts.