If the battery starts to swell, get it replaced and see what Apple quotes you. I delayed it (thought the fan noise was because of dust so i tried opening it up and shooting compressed air at it and that did not work but I did notice how hard it was to close it back up) until it caused the fan to non-stop whining at an unbearable rate.

Took it in for an official check up to double-check it as i was thinking about ordering fan parts to repair it myself. They said the battery looked to be swelling which they thought was causing the insane fan noise and quoted me $200 for the battery replacement. I thought I could buy the battery cheaper but grudgingly accepted as they said it would cover all the repairs with that fee. They shipped it to a repair center and then upped the fees by $100 for labor. I again grungendly accepted it as I just wanted it fixed, I could mess up the personal repair, and having them do it saves me time.

After getting the laptop back that looked brand new with all the replacements, I remembered why I love Apple. I'm just surprised they didn't tell me all the parts they were going to replace for the $300 as that would have sold me instantly especially considering my trackpad had been half broken but I did not associate it with the swelling battery at the time.