How to change heater core

My passenger floor mat is being covered in coolant and it is coming from behind the dashboard where the heater core is located. I would like to know the proper steps to take in order to remove the dash, like what exactly I have to remove, and how to remove it so I don't remove anything unnecessary. I also would like to know how the cover for the heater core inside of the cabin would come off because from what I can tell there are plastic rivets holding it in place