Well, immortality is a big step, but I think invulnerability is very important too. With both those in your hip pocket ....man oh man!
Dr Kaku says that a Type 3 civilization would be immortal.
A children's story: There was a woman who got a wish and wished for eternal life. However, as she got older she began to shrink like people do. They get shorter and wrinkle up. The older she got the smaller and more wrinkled she got. Eventually she was the size of a thumb and looked like a raisin.