Get the battery replaced at an official repair location rather than a middle of the food court business. Apple has a whole setup of gear that will get a perfect result pretty much every time. And they will just give you a new phone if they break it.
I do wonder how considering the iphone battery on iFixit costs $64AUD which doesn't even include the adhesive to reapply the screen. If you got one of ebay or similar, it's not a new battery, it's one that's been salvaged from a stolen phone and likely preworn.
Not an iphone, Lg G8s thinQ
was suprisingly easy to remove the battery cover, just need a blade and a hair dryer. The replacement battery is not original, could not actually find genuine part on sale. But it is a new battery, and they don't need to cost $50
I tried a battery replacement service once and didn't like the result on my sealed and hard to open by design phone.