Will you be able to attend the One-day Patient Conference in San Francisco
on July 20? That sounds pretty close to the target date for the transplant, but it would be a chance to learn a lot in a single day and meet some of the people who have traveled similar roads. My wife and I will be there and would be glad to talk to you. Perhaps the doctors there, all experts in bone marrow failure, will be able to make some sense of your mom's struggle for a diagnosis.
Is your mother in pretty good health overall? I hope so, because that helps lead to transplant success. How fortunate that sibling donors are available - twice as many as you need!
It sounds like you and your family are taking a sensible approach to this, preparing to make yourselves available and asking questions.
I hesitate to say that you should read a bunch of stories about the transplant experiences of other patients, because each patient's story is different and you don't know that problems another patient encountered will be problems for your mom. But I'll say it anyway - reading the stories of others helps familiarize you with the terminology, some of the commonly used drugs and procedures, and shows you that even the most successful cases tend to include some ups and downs.
Some people your mom's age want to know all the details about their medical care, and that's great (bring her to the conference if she's up to it). Others may want family members and doctors to manage their care and keep track of everything for them. You know your mom best, so try to judge how much of the details she wants to have and whether she should be the one to take notes on what the doctors and transplant team say, or whether you or your sister should be the recordkeepers. Since you've been at this for months, you probably have a system worked out already.
As the transplant date approaches, Stanford should give you printed information such as a checklist of what your mom will need with her, diet and nutrition guides, and so on. It's all very useful, but specific to that hospital.