Estate planning is "the collection of preparation tasks that serve to manage an individual's asset base in the event of their incapacitation or death, including the bequest of assets to heirs and the settlement of estate taxes. Most estate plans are set up with the help of an attorney experienced in estate law."
The first step in estate planning, when taking into consideration one's religious beliefs, would be to consult your spiritual adviser – a priest, pastor, rabbi, imam, etc. Discuss the religious options that exist for you and what they believe may be best for your family while going through the process. You can also navigate to this website to get more knowledge about estate planning.
A letter of instruction of last instruction should be written for your family and loved ones and religious issues should be addressed in your words, not with legal formalities. It should indicate what religious faith or faiths, or lack thereof, which you were raised as well as the faith that you are currently practicing.
It should also indicate your religious affiliations and general religious desires. Indicate the type of funeral you want, the type of mourning process to be observed and which religious customs, if any, should govern.
You may not be able to control what will be done when the time comes, but expressing your wishes will serve as an important guide to your family and loved ones. Make sure that if religious matters are important to you, your family should be made aware of them.