Need help re-installing Head Gasket

Hello All,
How hard is to re-install the head and gaskets for a 1990 toyota cressida
that was overheated. I have a new Gasket set and just brought back the head
from the machine shop.

Steps, directions and where to start are appreciated

Do I need to find out what caused the car to be overheated to prevent it
from happening again.


Thanks
Norm