First I would take off the heater hoses from the eng side firewall and replace em with some junk hoses and run some water thru the core to get all the antifreeze out to minimize the antifreeze mess on your inside parts/carpet (first put a thick towell under the box). Take the small thin plate/phillips screw that is on the firewall securing the nipples where they come thru the firewall (if it has one). On the inside I have no specific info I would just take off the cables and wires etc & possibly the glove box so you can work the heater box back & tilt it to let the nipples come thru the firewall