The important thing to remember is that prevention of gum disease is the first stage of treatment; making sure that you're cleaning your teeth, in between your teeth correctly means you're in good stead for the future and treatment success is more likely.
Treatment of gum disease when it's active is managed through non-surgical forms of deep cleaning which are relatively minimally invasive.
Other forms of gum disease treatment involve surgery, and this is often reserved when there are areas of gum disease which haven't responded to the simpler treatments. It's a painless process of treatment because more often than not your gums are numb, so you don't feel anything.
The important thing is to seek treatment as soon as you feel that you've got any form of disease or if your dentist informs you.