need advice on installing heater core

well i already have my dash out. I disconected the two lever for the box flaps undid the bolts and i lifted the flap up and i see the heater core behind the plastic wall. But how the hell u get it out of there? Or do i have to take that whole heater duct off the firewall? 89xj

thanks for the help nevermind. 5 bolts on the firewall and it all the heater duct comes off. Take the top off the box, take the bolt that holds the heater core tubes 2 the box then it comes out and reverse process.