I'm having a problem trying to get this object to be interactive in this environment I am building. When you approach a sign with this "wanderer_figure" I want a prompt to pop up within the GUI layer asking the player to press space to activate further text to be shown. Right now I have it coded as such:

var showGUI : boolean = false; 
var customGUI : GUISkin;

function OnTriggerEnter (myTrigger : Collider) {
    if (myTrigger.gameObject.name == "Wanderer_Figure"){
       showGUI = true;
       }   
}

function OnTriggerExit (myTrigger : Collider) {
    if (myTrigger.gameObject.name == "Wanderer_Figure"){
       showGUI = false;
       } 
}

function OnGUI() {
//activate custom skin settings/textures
    GUI.skin = customGUI;
    if(showGUI){
       GUI.Box (Rect (Screen.width/2-100, Screen.height/2+200,200,100), "Press SPACE to Interact");
    }

    if (Input.GetKeyDown ("space")){
       showGUI = false;
       GUI.TextField (Rect (Screen.width/2-100, Screen.height/2+200, 400,200), "TEST");
    }
}

However, when I try and test this code, the second half of the GetKeyDown call doesn't work, even if I hold down the space key. I'm trying to see what the problem, and also am wondering how I might make this second set of text disappear after a certain period of time (or else disappear based on more user input).

I'm kind of a n00b at this, so any help would be greatly appreciated, and thorough explanation of any tips would would equally be extremely helpful!