I would try a new HDD before removing the cmos battery. I know with desktops removing the cmos battery no longer clears bios passwords. However I believe you HDD was encrypted. If there is no important data on it. you can hook the HDD to another pc and perform a low lvl format to try to clear it out.
usually the bottome of the pc has 2 easy access doors. one for memory and another for the HDD. Usually if you look real close they have symbols by the screws you need to remove. usually it's only 1-2 per door.
If your still intent on removing the battery, you'll simply have to remove every screw and pull it apart. I recommend getting a multi sectional tray and keeping the screws relative to their location on the laptop.