The beginning and not sure what to expect.

My dad just got diagnosed with stage IV melanoma last month after breaking his femur due to a tumor that had weakedned it. It feels like we've been getting information piecemeal and we're at the point where they're trying to  figure out what kind of treatment he is a candidate for. It's been my sister and I that have taken him to radiation/doc appointments and his girlfriend who has been living with him and watching him at home since she doesn't work. He had to spend two weeks at a rehab facility for OT/PT on his leg and he absolutely hated it; I think he went home too early, because when he got home he fell again and fractured his rib. My sister have already learned that we cannot leave it up to him to schedule a nurse and physical therapist, but every time we've tried his girlfriend has kept them from entering the house- it's been a week and a half since he's had PT and has severely declined. We may have an elder abuse problem on our hands with his gf,  but it's been unclear whether it was her or my dad refusing to let them in. At this point, his girlfriend has  been having multiple break downs, yelling at doctors, and screaming at my sister and I. It's been so tough on all of us and even harder that she's been projecting her own grief. She's looking to move out because she can't deal with it anymore. I'm trying not to demonize her because it's just as hard on her as the rest of us, but my tolerance for her behaviors is starting to dwindle.

Anyway, I guess I just feel overwhelmed that this is just the beginning. I feel angry because I feel too young to be dealing with all of this at 28, and guilty because that's my dad and this could be happening to me at any point in my life... maybe i should feel grateful that it didn't happen earlier. But I have my own hopes and dreams of starting a family and my career is at it's start and I feel selfish for not wanting to go in to help my dad 100%; I'm also angry with my dad because he keeps refusing care from nurses and home aides and making things harder on himself and the rest of us. My sister and I are grappling with having to stay with my dad and take care of him- help him get dressed, cook, clean, etc, but I don't know if I'm cut out for helping him bathe or clean him after bowel movements. I feel TERRIBLE for saying that because he dealt with me as a infant but at what point does he need full care from a rehab again? I don't even know if I can lift him! 

Maybe this is too much for a forum and I'm considering in person support groups. I guess my question is, what are some things that I should expect in this journey? Do I need to put my life on hold where I can and just get over it? And how can we set boundaries with his girlfriend? How can I help while still maintaining my own life?