An item in my calendar

Psyc assessment. June 2nd. Finally. Its booked.
For some reason this appointment isn't... resonating (I'm not even sure if that is the word I would use to describe what I'm feeling, but its the best one I can find at the moment). I'm not nervous, apprehensive, or feeling much of anything towards this appointment right now. I thought I would. I mean, I was a bit nervous when I had the meeting with the social worker, but that went really well, and now with this, its just an item in my calendar.
I'm sure they will check to make sure I know what I'm doing, that I'm doing it freely without coercion or compensation, and things like that. I think they will go through and check to see if I am mentally competent enough to know what I'm doing, and am emotionally stable.
My understanding (although I may be mistaken) is that this will also be a time to discuss my wishes, i.e. personal directive.
So what will I say to them if/when this comes up? I don't want to be a vegetable, I don't want to be a shell of a person, unable to engage in meaningful interactions with family and friends. I don't want to be kept alive on life support without reasonable hope that I will ever be able to eat/breathe on my own again.
In all honesty, what I want is to go for surgery, have it go wonderfully (I really need to stop watching Grey's Anatomy), and recover free from complications.
But I understand that this might not be the case, and the best thing I can do is be prepared for it.

If they get into why I'm doing this I'm not sure what to say. I'm doing this because I'm young, healthy, and able. I don't know anyone who has kidney disease or suffers from organ failure of any sort. I don't know anyone who needs or has ever received any sort of organ transplant. I have no connection to this "industry" at all. I'm doing it because I can. Why does it worry me that this is not a good enough answer? I guess I'm not really worried, but I just don't want them reading anything into this and preventing me from donating. For whatever reason donating has become more important to me than I thought, and I would feel a failure of sorts if I was unable to donate.

June 2nd. 2pm. Calendar marked.