I am my father’s General Power of Attorney/Agent (Attorney in Fact) and have…

I am my father’s General Power of Attorney/Agent (Attorney in Fact) and have the power and authority to perform or undertake any actions he could perform or undertake as if he were personally present. My question is: This Power of Attorney document appoints one of my sisters as my successor, and I would like to know if I have the authority to have that document changed to appoint our other sister as my successor. My father is 92 and has been having quite a bit of short term memory loss over the past year. My current successor is in financial difficulty, as well as her offspring, and I feel I am responsible to protect my fathers assets to the best of my ability and would like to see that carried out to his wishes should something happen to me. Thank you!

Wills,codocils If you change a will by changing addresses must this be…

Wills,codocils
If you change a will by changing addresses must this be typewritten and witnessed? If witnesses needed, do they sign by the address chages or at end of document and reference the address changes they are witnessing
If you added page numbers is this a codocil?
I also changed a portion of the estate going to an in-law? Is this witnessed the same as above.
Does the procedure for above also hold true for General Power of Attorney and Advance Health Care Directives.