My MacBook Pro flashed up a 'Service Battery' warning. A check a my local Apple Reseller, (no official stores here), came up with a huge fee to get it done. US$90+ in labour costs, + battery + other; total cost US$290. Crazy.
Enter iFixit, US$150 incl shipping half way around the globe. 2minutes to swap it out. Done.
Lucky I did too, the old battery was out of shape - a fire hazard for sure.
Super super easy. Literally 2 mins.
Don't pay Apple ; do it yourself. Why would you not?