heater core replacement

whats involved in replacing heater core on a 1991 z28 and what do i need to take off to get to it? thx for your help

First get the hoses off of it in the engine bay. They are back behind the engine on the right side going to the firewall.
Drop the passenger side kick panel. you'll need a nutdriver handle and extensions and a universal joint & 9/32" socket and a flashlight. Find all of the screws on the plenum box. There's a few up atthe top of it which you'll need the universal joint for. Remove the plenum box lower cover. Then towards the center of the car you'll see the heater core. there'll be some more of those 9/32" head screws holding it in place, remove them. Place an old towel or 2 on the passenger floor and carefully remove the heater core.
Assemble in the reverse but have someone to help put the hoses back on the core while you push on it to keep it in place.

whats involved in replacing heater core on a 1991 z28 and what do i need to take off to get to it? thx for your help
do i have to take the whole dash off? and where is the 9/32 nut located at the top of box/ thx

do i have to take the whole dash off? and where is the 9/32 nut located at the top of box/ thx

No, not the whole dash, justthe underside kick plate. The screws on the top of the box you'll have to feel for. I think there are 3 of them.