Might possibly consider replacing my eyes/ears if either goes out, and they have the technology. I would probably stop there. I would not unnaturally prolong my life I think, although if it's something simple, I don't know. But if I got to the point where my quality of life went way down, I would just accept death naturally.
Imagine, everyone you know dying, while you're still alive. Immortality is as much of a curse as it is a blessing I think.