Buck,
It does sound serious and you and your grandfather have my prayers. But he aint gone yet my friend, keep your head up, trust in the Lord. Who knows what may happen?
If you can get him home and feeling good enough this spring, load him up and take him to the woods one afternoon for a look around, build a small fire and enjoy it for a couple of hours. My grandfather and I was close also, he died August a year ago. I'm sitting here now with a big 'ol smile on my face just thinking about that man. I sure do miss him.