You should really try to get information from the doctor rather than here. That said, MRSA stands for methicillin-resistant Staphylococcus aureus; it is a form of "staph" that is resistant to the antibiotics usually used to treat infections. It can be treated however. Certain meds are still useful, and superficial abscesses can be drained.
It can be fatal, but a majority of cases are not so serious. I would definitely get in touch with them to find out exactly what the doctors said. Family members tend to make things sound a lot worse than they are.