If that's the same battery that's been sitting in that bass since it was built, then yes, change the battery. While you're there, make sure the contacts on the battery clip are free of corrosion.
And since this bass has been unplayed for so long, you may want to exercise the jack and controls. Plug and unplug a phone jack twenty or thirty times. And rotate all of the controls back and forth through their full travel twenty of thirty times.