I am sorry for your loss.
1) Retirement accounts are NOT part of the estate.
2) $10,000 a year can be gifted tax free.
3) Make sure you have all titles someplace and be ready for paperwork.
I hope that this will be simple transfer of assets and not turn into the nightmare of MINE MINE MINE and attorneys and law suits.
Other things to have ready
1) Will
2) DNR/DNH Do Not Resuscitate and Do Not Hospitalize; needs to be signed by primary care doctor (if relative is at home)
3) Hospice Get signed up NOW!!! It will be pain management. These people have the hearts bigger than Alaska. (if relative is at home)
4) Funeral Home arrangements. Especially if relative is at home; when your relative passes you will have to call 911, the police and fire/emt will arrive. When they leave, and you have a case number, then call the funeral home for pickup.
5) Death Certificates, everyone wants a death certificate. If there are multiple people on a title, and they have both passed you will need one for each person.
I know this is more info than you may need, or want.