Heater Core removal 90 Grand AM

I am writing in reference to the removal of the heater core on a 90 grand am. I followed the instructions that were sent to me referencing the auto zone step by step procedure. However, I am stumped at the removal of the hoses. These hoses are against the firewall, they look aluminum vice rubber and what tool do I use to disconnect them? Can I do this from above? Also, I have the cover that hides the heater core loose but it won't come apart from the firewall from inside the vehicle. I know that I got all of the screws because it took me an hour just to get the last one that was up against the wall. Please help. Is it stuck due to adhesive? Please help. thanks.

Terry

I use the universal tool, plyers.
Unless its a screw type, then a straight slot screw driver.

When that fails cut & replace the hoses.

On the heater core housing, its just attached with sealant.
Make sure you get all the screws too, thiers 1-2 at the very bottom by the floor.