It's not hijacking the thread by a long shot, Clay. We've all either been there, or will likely have to face this some day. My last time of facing this was three and a half years ago with my mother and it went along the same lines as James' mother's journey, but a bit faster.
This message is one I sent to James via Email a couple of hours ago. I can only hope that it helps you or others in a similar situation face the passages ahead:
Get whatever rest you can. You'll be emotionally all over the place for quite a while, no matter what happens now. There's a feeling of emptiness mingled with pain beyond anything that you have ever imagined that has no doubt set in. It will get better when she finally passes, just for a bit, since that is a resolution to the situation and your inability to do something has also come to a close, because she is now in the best hands possible. But then the pain and emptiness comes back, as you feel like you're mentally going from room to room, looking and searching for something, but not finding it. You'll figure it shouldn't be like that, because you knew it was coming, was for the best under the circumstances, and for any number of other reasons.
Probably the worst is looking at things. Things that she had. Things that she used. Things that you realize don't represent her at all, but do represent a life that no longer exists for any of you. I'd suggest closing off her room and her things for a couple of days until you can cope a bit better. Not that it will be that much better in a couple of days, but you will have a tiny bit of perspective by then. Before you do that, choose the dress or outfit she would most like to wear and whatever other items she might want to have for her final rest, or delegate to [your wife] and the girls if you feel it's more appropriate. Perhaps [your yongest, preschool-aged daughter] can even make her a card or picture to take to Heaven with her, so [your youngest daughter] feels somehow that she has been helpful to Grandma.
You'll reach a point of dullness inside finally, or so it seems, but the hurt goes on all around that core of dullness for a very long time. Expect it to go on slowly receding for a year, and then finally getting to a point where you feel you have reached a state of healing yourself, or at least true acceptance in two years. It's a long process and it is not helped if you beat yourself up over what might have been along the way. Be grateful that you had a chance to be with her and that it is not a situation where, like some families, the loved one walks out the door with words left unsaid, and they never return again.
The understanding I got from my mother as her spirit left, was that none of the petty emotions that we have on this planet matter anymore. There is no resentment for words that either were said or went unsaid. There is no anger, no ugly emotions at all - only a supreme happiness and total peace that leaves no room for anything but love. Your mother will understand totally how much you love her and always have, and she will be shed of all the earthly issues. It is up to you to rid yourself of any feelings that you wish things had worked out otherwise or that things had gone differently. Whenever you catch yourself thinking that you wish you had said or done something different though, know that she understands entirely that we are human and that you did your best, and it was done with love, so absolutely nothing else matters. She has an understanding we are incapable of now since she has risen above those emotions. Your mom is probably already feeling the call and is experiencing the extreme peace that sets in. It will be a blessed relief for her when she is finally able to leave entirely. You, on the other hand, will likely be a wreck for a while. Get rest and find your inner core of peace so that you will have some to share with your family too, as they each grieve in their own way.