There's also the prospect of what exactly will you be able to do with it if it DOES still work; While for some of us, sexual desire has decreased with age, the other problem is, if it hasn't, who do we have available to have sex with? I discovered a while ago that it wasn't my libido that had died; it was that I was surrounded by old unattractive females. When a hot young woman smelling of perfume walked through my department one day, I once again felt the flag raising spontaneously. My sex drive wasn't dead, and my desires weren't decreasing, there was simply nothing around to get aroused about. And that's still the problem, at least for me; there simply aren't a whole lot of women that turn me on, that want me for a mate as well. There's some bizarre myth that as we get older, who we want to have sex with, changes as well. Yet, I don't know a whole lot of men who are actively hot for old ladies (there's one, but he's always liked much older women).
Before the current state of the art procedure which uses the penis as parts for the newly conversion to a vagina, there were other methods using skin grafts from other parts of the body, or even a section of intestine inverted (problem with that is continuous mucous type secretions, though I guess you could always just wear a pad or tampon or something; up side was, natural lubrication). You don't need either the penis or even much of the scrotum to make a nice set of female genitalia. Plastic surgery has come a long way.