assume he is able to
He's not. He has a hypothesis that is being bashed all over by other experts in that field. Half of the criteria he needs to meet to even be able to attempt this have not been met by modern medical science. Like, say, re-attaching a severed spinal chord, let alone attaching someone else's
who am I?
_You_ are dead. I would claim the "head" determines the identity of the person. Thinking otherwise, I think, betrays magical thinking.
I am a woman and have the head of a man fitted! I wake up to find I don't have a penis
Once again, _you_ are dead, the man wakes up and finds he doesn't have a penis. He should feel lucky he woke up at all. Besides, haven't we all wished we could experience this anyway?