I really am sorry about your Mom. I had never heard of this type of Cancer until my Grandmother ( she was 83) was diagnosed the end of Sept 08.
I remember asking the same question you did. " What's next? What do we expect? Will she be in pain?" Its a helpless feeling.
My Grandmother stayed in her home until 4 days prior to her death. At that point we were fortunate enough to get her into a residental hospice. We had been doing the care ourselves and with the help of a family friend and a Nurses Aid that would come in for bathing. Oh, and a nurse that checked in every few days.
They did end up giving my Grandmother something for agitation a few times. I couldn't tell you what. My grandmother was severely diabetic. Looking back I feel some of her agitation came from diabetic shock due to the fact we could no longer give her insulin with any results.
I can tell you this ( and this is just my experience.) The last few days were relatively peaceful. Her pain was under control and she slept a lot. ( Again, maybe from diabetic shock or just from the large amount of drugs?)
However the things that scared me were this: She would kick off her covers and kept trying to speak. I couldn't understand her and that made me feel bad. She did halucinate a few times. I had to lie to her and go along with what she was saying to calm her down. (i.e. She thought she was at her condo and it was flooding. She wouldn't lie back down in bed until I promised to turn the water off. Of course she wasn't in her condo and there was no water) There was also a time where we really had to work hard to get her to stay safe in bed. She kept trying to get up to "walk to heaven".
We got a really good pamphlet on the stages of dying. It broke things down into a rough time line and gave us an idea, based on the clues her body was giving us, how much time she had left. It was very helpful. I think most hospice programs have something similar. The last day she slept mostly. Her breathing became more labored. She passed away 12/18/08. It seemed so long but so fast.
I hope none of this was to much sharing. I can't over state how different everyone is. I really am sorry you're having to go through this.
The best thing I did was talk to her before she got really really ill. We told each other we loved one another. I asked her questions I'd wanted to ask her. We cried about how unfair it was. I'm glad I didn't put that off. As the disease spreads they become tired and more medicated these conversations can get difficult to have. The sooner the better.
Take care of yourself and your family. Love each other.
All the best,