It is a simple swap. Just get the entire heat only system and it just bolts in. When I got mine, I left the heater controls attached to the inside heater box. No losing parts. Then just pull the fan box from the engine compartment with the wiring and you are golden.
A couple of suggestions.
Get a new heater core. Cheap insurance.
Be sure to get the factory heater box wiring loom. It comes from the fan switch, through the firewall in a large rubber plug/grommet, then ends at the fan motor. Flat multicolor wire that looks like trailer wire.
Cut a hole in the firewall under the new heater box housing (covered by the housing when installed) , right side under the resistor about 3" x5". Since you will have made a block off plate for the old ac system holes in the firewall, your heater needs a place for air to enter the system. Otherwise, you get lots of fan noise but no air movement (ask me how I know).