My mom is going in tomorrow to have a stent put in her heart or arteries. Is this a dangerous procedure?

Yes, it is. Coronary stent risk is variable, but mortality risk is about 1 to 3 per hundred on average. Just make sure her cardiologist discusses the specific risks with you. She needs to balance the risks and potential benefits of having a stent or having bypass surgery or using medications. Her cardiologist is the best person to explain it.