Hi...
MRSA's not a disease, it's a bacertium that can cause all sorts of different diseases. And any disease that it causes can also be caused by its cousin plain old Staph A. So you'd never know your problem was causes by MRSA until you had the bug cultured. For example, it sounds like the previous poster had MRSA follicultis and developped an abscess. But other bacteria can do the same thing.
Many people are just colonized with MRSA. It lives happily in their nose along with many other bacteria. When it gets someplace it shouldn't, it can cause a wide range of problems from localized skin infections to meningitis and sepsis.
Any staph infection needs to be treated, however, whether it's MRSA or not. MRSA will just be more difficult to treat.