When my mid-2010 MBP needed a new battery, I looked the replacement procedure up on iFixit, and I felt comfortable that I could handle it myself. However, iFixit was out of stock on batteries, and noplace else could get one to me very quickly (without breaking the bank), so I took it to an Apple store and had them do it. Solely because I could be back home in four hours with a new battery vs. waiting up to a week to get one via mail order.
I don't remember the exact figures, but it was something along the lines of $125 to order one and $135 to have Apple do it (or if that's wrong, the concept is right). So not a huge premium (not counting gas to Apple store and back if you are far away). In other words, probably a no-brainer if you are not comfortable doing it yourself anyway.