Free is a good price to pay, & if battery does fail, cut the both ends off and save.
Never open a Lipo till you understand the dangers, get some one to assist with knowledge or read up before you attempt to open. I can tell you that the plastic film that separates the battery material is thin & if damaged allowing the two internal cells to short, It's Flower Pot Time, as this lithium material is volatile.
If your not so great a solder I would ask some one local who is to help. You will get more life from a battery balanced. Typically new you get 500 charges, that's running once a day for almost a year and a half. Charging, storage voltage, never venturing below 3.0v or 6v for a 2 cell, are all important factors to a Lipo's life span as well.