Building a Face Generator, need to destroy previous instance after pressing key a second time

I am building a Face Generator, everything works fine but my problem is that every time I press Space Bar it makes the randomized elements appear on top of one another, I need a way to destroy the previous face once the key is pressed a second time to generate a new one. I'm not sure how to proceed!! Thanks for the help!!

Code:

 using UnityEngine;
 using System.Collections;
 
 public class GeneratorScript : MonoBehaviour {
     public Transform spawnhats;
     public Transform spawnfaces;
     public Transform spawneyes;
     public Transform spawnmouths;
     public Transform spawnbackgrounds;
     public GameObject [] eyes;
     public GameObject [] hats;
     public GameObject [] faces;
     public GameObject [] backgrounds;
     public GameObject [] mouths;
     private bool faceAppeared;
 
 
     // Use this for initialization
     void Start () {
 
         faces[0]=GameObject.FindGameObjectWithTag("face1");
         faces[1]=GameObject.FindGameObjectWithTag("face2");
         faces[2]=GameObject.FindGameObjectWithTag("face3");
         faces[3]=GameObject.FindGameObjectWithTag("face4");
 
 
         eyes[0]=GameObject.FindGameObjectWithTag("eyes1");
         eyes[1]=GameObject.FindGameObjectWithTag("eyes2");
         eyes[2]=GameObject.FindGameObjectWithTag("eyes3");
         eyes[3]=GameObject.FindGameObjectWithTag("eyes4");
 
         hats[0]=GameObject.FindGameObjectWithTag("hats1");
         hats[1]=GameObject.FindGameObjectWithTag("hats2");
         hats[2]=GameObject.FindGameObjectWithTag("hats3");
         hats[3]=GameObject.FindGameObjectWithTag("hats4");
 
         backgrounds[0]=GameObject.FindGameObjectWithTag("back1");
         backgrounds[1]=GameObject.FindGameObjectWithTag("back2");
         backgrounds[2]=GameObject.FindGameObjectWithTag("back3");
         backgrounds[3]=GameObject.FindGameObjectWithTag("back4");
 
         mouths[0]=GameObject.FindGameObjectWithTag("mouths1");
         mouths[1]=GameObject.FindGameObjectWithTag("mouths2");
         mouths[2]=GameObject.FindGameObjectWithTag("mouths3");
         mouths[3]=GameObject.FindGameObjectWithTag("mouths4");
 
 
 
 
     }
 
     // Update is called once per frame
     void Update () {
 
 
 
         if (Input.GetKeyDown ("space")){
 
             faceAppeared = true;
             Instantiate (faces[Random.Range(0,faces.Length)], spawnfaces.position, spawnfaces.rotation);
             Instantiate (eyes[Random.Range(0,eyes.Length)], spawneyes.position, spawneyes.rotation);
             Instantiate (hats[Random.Range(0,hats.Length)], spawnhats.position, spawnhats.rotation);
             Instantiate (backgrounds[Random.Range(0,backgrounds.Length)], spawnbackgrounds.position, spawnbackgrounds.rotation);
             Instantiate (mouths[Random.Range(0,mouths.Length)], spawnmouths.position, spawnmouths.rotation);
         }
 
     }
 }