Both my father and my sister are Illinois residents and I live in West Virginia. Would an Illinois form be used or a West Virginia form? Both my sister and I are designated as beneficiaries on everything and I'm fine with her taking care of all matters. I understand from just briefly reading that some states require different things and will only accept certain forms. We would like to do this right the first time around because I truly cannot afford the price of a lawyer. And again, we're both wondering if she needs to make out a form and send it to me for signing and notarizing or if I'm the one who makes out the POA .
If for your father, a Power of Attorney is only used if the person is alive.
Did your father have a Will? If yes, then the Will will say who will be in charge of doing of he financials. If no Will, then your sister would need to make an appointment with the County Probate office and the probate office will assign her to handle the probate. Yes, it is complex.
Your father's POA is invalid after his death, so transferring your proxy under the POA isn't valid.
It really depends on who's named in the Will to handle your father's estate.
Do you and your sister have a good working relationship?
As GardenArtist and I had mentioned, one cannot change Power of Attorney for a person who has already passed. The POA died along with your father. I know these legal documents can sound confusing, what is needed, what is not.
Does your sister mind doing all this on her own? Did Dad live with her or on his own? Along with the grief, there is so much to do. She is probably dealing with the funeral. Next all the legal paper regarding his estate. Plus clearing out Dad's furniture and personal items. It can be very exhausting.
As to your question, since there is no formal documentation limiting handling his affairs and assets to either of you, AND if you don't have to file for probate, I don't see why you can't work out between the two of you what each of you wants to do.
If there are assets not titled jointly with rights of survivorship, state law on intestacy (dying without a will) would govern distribution of assets.