Hi @sarravo
Here's the maintenance and service guide, taken from this support webpage for the laptop.
Go to p.38 (p.50 of 99 pdf) to view the procedure to remove replace the battery.
Here's a supplier that may help, depending if the cost is acceptable to you of course.
Alternatively search online for 922976-855 battery and check if you find other suppliers that are more suitable.
It is not advisable to run the laptop directly on the charger without a battery installed.
When working inside a laptop, make sure that the laptop is turned off and the power is disconnected. Then disconnect the battery from the motherboard i.e. as soon as it is accessible before doing anything else. Doing this will minimize any potential electrical problems from occurring if you happen to touch anything you shouldn't. There's always power on the motherboard somewhere, even when the laptop is turned off. The power button is not a power isolating button.
Keep a jar/container nearby by place in any screws that need to be removed. Use a different jar for each set of screws removed e.g. back cover screws, battery screws so as not to mix them up or lose them.
Also wear a wrist strap connected to an earth point so as to not cause any ESD damage to any sensitive components that you may touch.
Lastly take your time. I'm sure that you'll be fine