What I learned from phone repair bros - unless you got a fruit phone (require laser alignment for case reassembly for perfection) all other phones they repair, open case, remove and replace batt, close case, is all done 5-7 minutes. I myself see them do it.
Don't restrain yourself from using your dear phone by trying to baby the battery. If battery louya, just change it using one of the shops in SLS, if you need any recommendation, I do it at Apps electronics in SLS many times already, the price is quite cheap, comparable to the cost of buying a battery off the shelf.
I understand, last time I had HTC One, I suffered for months with a louya battery spoilt by big heat caused by me putting my phone on car mount in the sun. How stupid I was. Now I just go SLS repair shop and change batt all happy happy.