I am about 10 months in to a similar experience, pre-diagnosis, and I can echo your statements about how terrifying the unknown can be. Being surprised to wake up in the morning can really alter your perception of reality. I think there is an enormous amount of abstraction needed in this perception to avoid going insane. I think it is important to be able to remove oneself from the reality of ones own mortality and I don't think it is possible to live normally while being too aware of it. Having said that, If recover from this whole thing I think it would ultimately be a good thing to have gone through as my appreciation of normal life would be much higher.
Hehe wow it's funny to see my words written by someone else, I've come out of the other end of this, for three months I'd be surprised to be alive in the morning after nights of wakin up to chest pains (when I was 22 and relatively healthy). Like everything it can change you, it gave me a different way of seeing the world and I can slip back into that cold mindset to consider things when I need a bit of distance. It also gave me even more appetite for doing fun things and staying true to my natural, childish disposition :)
I'll never forget the ceiling of the apartment I spent so many nights waking up in pain seeing, or the sun shining on the wall in the mornings as I thought "oh, I'm alive!"
Good luck for your surgery.