Starting Bone Marrow Transplant

My son is being admitted in the hospital tomorrow  to start his chemo and bone marrow transplant.  
I'm so scared for him ! !   He will be on three different chemo treatments and methrotrexate for a few days..  The doc's say 40% of
people don't make it through.  
Does anyone know what the chances are with AML?  
Has anyone gone through a bone marrow transplant?  
Is it very difficult pulling through it?
The doc's say he needs a good attitude about this or he won't make it.
So afraid of losing him.  I searched all over the internet to find someone who went through this, and try to get some
tips, that I may be able to help him through this, but couldn't find any information or support.  He feels like he's all alone.