It is good to be scared but this is a very well proven procedure. Using the cadaver bone will save you the pain of having a small procedure on your own hip to get bone for your procedure. More surgeons are going to the cadaver bone because patients have been suffering extra from bone removal too.
You may want to talk to the doc before the surgery about the possibility of having the "bryan" artificial cervical disc replacement vs. Fixation at the c5/6 site. It may not be possible because you are going to have c6/t1 fused as well.
Your recovery is going to be very painful and you are going to have to work hard to make it happen. If you slack, it will be evident by your recovery. Certian modalities will come back regardless of pain, you need to work to help yourself. There is no guarentee that you are going to get better, but you should get some mobility back.
My l5/s1 charite artificial disc replacement worked for the disc pain but now I have to have nerves destroyed some time later so I am a 50/50 case.
Also make sure before you let this doc work on you that if you have a bad time healing, that he is not so pompous that he will not refer you to a pain management doc to help with pain if the proccedure is not perfect in the pain department. Make sure he knows you do not want to leave his practice because he has his mark on you for life, but pain is not his practice, fixing is and he needs to have compassion for you post-operatively.