My battery was running out too quickly. Had to charge my phone at least 3 times during the day. The fg_fullcapnom showed the capacity to be 1145, instead of 3000mAh original capacity.
YouTube was a big help. I used their complete detailed guide to replace my battery. It went perfectly well.
However, the new battery is equally $@$*. I wiped my cache and discharged and charged the battery several times to ensure correct calibration. After 12 cycles the fg_fullcapnom now shows the capacity to be 1012 (!!??). Since the battery is not OEM, I am now regretting buying from ifixit.
The kit did not come with any written guides. The published guide and the youtube video published by ifixit are incomplete. They only show the teardown and say go in reverse for the rest. Nothing about how to use the adhesive or make sure that the phone is water resistant again.
It cost me $43 to buy the kit and the battery including taxes and shipping. Samsung store near me charges $90 to replace my battery with OEM battery without any hassle. I think since it's not that much more to replace it with OEM battery, everyone should skip ifixit and go for the real thing. If not, try ebay, they have OEM batteries (at least advertised).