It all depends on whether you do it yourself or have someone else take care of the paperwork. In addition you should check the laws for where you live.
Some places allow for what is called the "usage method". Essentially the individual gets their name changed on their drivers license and from then on only uses that name. However in my opinion it's best to legally file a name change. This gives you a certified document to present if ever needed. The best place to start is by using Google.