Can someone tell me if you have to go to school for doing hair for the dead

No respectable funeral parlor will hire an unlicensed beautician, even for the corpses, as people do pay a lot of money for funeral services.

You will need to go to school and receive a cosmetologist licence if you want to work on people's hair and make-up. Most salons and morticians don't hire unless you have a cosmetologist license.