Will narcotic overdose kill me if I don't get treatment?

Can do. Overdose of narcotics can suppress or arrest breathing, then your brain lacks oxygen and u die. Needs urgent treatment with "anti-narcotic' medication.
Quite possibly. It's called an overdose for a reason. Big risk is to stop breathing or lose consciousness. Many celebrities have died as a result of prescription narcotic od. Regulation is a hot topic in pain management now. Only solution is er or ambulance for reversal agent or airway management asap. Also, avoid taking alcohol as the sedative effects can lead to unintentional od.