If all parties are in agreement to change of custody, what paperwork do we need to file to make this happen?

My ex-wife and I were divorced in San Diego county but now reside in separate states (I in OR, she in KS). When we initially divorced my ex-wife attempted to sneak out of state to file for a change of jurisdiction without my knowledge. This was uncovered and my lawyer, at the time, got a judgement to retain CA jurisdiction until my children turned 18. She recently requested that I take full custody of my now 16 year old child, who is in agreement with the change as well. Since all parties agree to the change, it seems to me that it should be a fairly simple matter of filing the appropriate paperwork. Is this assumption correct? If not, what do we need to do and if so what paperwork needs to be filed and where can I get the right forms?