(FYI -- this isn't a reply to whisky's post, I was typing it while he posted and they seem to hit similar chords)
My mother passed after a long illness over 25 years ago; 8 years later my dad passed suddenly in his sleep.
It doesn't matter which way they go; it's the biggest gut punch you'll get in life either way.
Ultimately, the most comforting thing someone said to me is, "It's not something you get over. It's something you learn to live with." That sounds a little gloom & doom on the surface, but it's a life truth that actually helped me understand the grieving process. You grieve when it happens, but it's not out of your system. I can remember suddenly crying out of nowhere a year later, but then I understood why, and when I was done, I went on with the day. (This was all pre-TrekBBS so I only had an Elvis Costello mailing list to pour my heart out to on the internet, lol).
Don't forget to take care of yourself through all this. Let yourself feel everything you need to feel. And once in while, just sit and take a few deep breaths for a minute or two. It really does help the mind & body.