My daughter is 12 and we would like to change her last name to mine not her fathers anymore he is not in her life and has not been for years so if we do would we need him to help or can it be done ourselves

In gerneral you will need to seek the bio fathers approval unless there is a different father named such as a legal father. If you can't agree on a name change then it may not take place. Also it will depend on reasons a name change is requested as well as the impact on the child's life. A 12y/o has already established records and already has a reputation of sorts being called by a given name.

You will have to show that you have tried to serve notice of the change to the father.