Does anyone have any experiences with watches?

I got a $100 watch as a gift about...3-4 years ago. It's a G Shock. I haven't used it in a while (Not stored in light )and it's not showing the time. It's just pitch black. I think the battery is dead but I don't know how to change the battery. I don't know if I can send it to the company to change the battery or not. It's still shiny and looks brand new because I take really good care of it. I would look at a manual but seeing it's been a few years, I do not have it anymore. Thank you.