15 - 45 minutos
My macbook pro 17's battery had 2.5 years of good use with 300 cycles, and was down to 80% health. It was just not staying on for that long, would die out on sleep mode, instead of resisting like before. So I purchased a new battery and replaced it for a new, A Stock battery from ifixit.
It was really easy, the guide was very helpful, specially because they had sent me the right tools. Took less than 20 min to repair.
After you get the new battery, charge it to full (you can use it) and let it drain completely (until it shuts down by itself). Then charge it back to full (I wouldn't use it, leave it off) to have a calibrated battery.