public GameObject spawnObject; // assign the prefab you want to spawn after X time.
public float spawnTime = 50; // time after which spawnObject is spawned

public GameObject[] destroyObjects; // Objects to be destroyed when spawnedObject is spawned.

void Start()
{
    Invoke( "SpawnAndDestroy", spawnTime );
}

void SpawnAndDestroy()
{
    if( spawnObject != null )
        Instantiate( spawnObject );

    if( destroyObjects != null )
    {
        foreach(GameObject destroyObject in destroyObjects)
        {
            Destroy(destroyObject);
        }
    }
}

Untested.