The school I work for had an old 13" MacBook Core 2 Duo in Black that was randomly forgetting the time and date, one minute it would be accurate, the next minute it would reset to January 1, 1986. So I decided to change out the PRAM battery to relieve that.
The process took me a couple of hours (it is a 39 step repair guide!). I had one of the battery tray screws strip on my when I was trying to take it apart, so I took it out with a file and a pair of snips
Watch those battery tray screws and be careful with them, they are super soft and will strip for no reason.