Well. My grandmother's death certificate finally arrived in the mail today. And apart from the fact that she died in my father's house (I am pretty sure he said she died in her hotel room), the most revealing item in the record was simply that she was cremated. Because cremation is considered "final disposition," there is no further record as to the location of her remains. They could be in a vault, or in the possession of my father's children (along with the remains of my grandfather and my father.)
Which means I have to contact my stepmother and ask her where the remains are located, something I was hoping to avoid.
I hope the urns are in a vault somewhere, but I won't be surprised if the family never allocated funds for such a thing. Since Carol has remarried it seems safe to assume she's not keeping these urns under the bed, or on the mantle. But my half-siblings are in Minnesota, Indiana and Wisconsin respectively; it's possible my stepbrother is in the western suburbs somewhere. I don't think I have his current address. Otherwise, I'd ask him. He of all of them has some affection for me, I think.
I'll send Carol a letter tomorrow. I hope this works out. She doesn't hate me anymore, I don't think; but she has never treated me like a member of the family.