Mixing together 2 scripts?

If your 'Mix together' is really all you want, then there's nothing more easy.

 #pragma strict
  
 public var floatSpeed = .5;
 
 static var selectedId : int;
 static var speed : int = 90;
  
 function Update() {
   if (Physics.Raycast (transform.position, Vector3.down, 5.0)) {
  
             rigidbody.transform.position += Vector3.up * floatSpeed * Time.deltaTime;
             rigidbody.drag = 20.0;
   }
   else{
     rigidbody.drag = 1.0;
   }
  
   if (selectedId == GetInstanceID()) {
        if (Input.GetKey (KeyCode.UpArrow)) transform.Translate (Vector3(0,0,1) * Time.deltaTime*speed);
        if (Input.GetKey (KeyCode.DownArrow)) transform.Translate (Vector3(0,0,-1) * Time.deltaTime*speed);
        if (Input.GetKey (KeyCode.Space)) transform.Translate (Vector3(0,1,0) * Time.deltaTime*speed);
        if (Input.GetKey (KeyCode.LeftControl)) transform.Translate (Vector3(0,-1,0) * Time.deltaTime*speed);
        if (Input.GetKey(KeyCode.RightArrow)) transform.Rotate(Vector3.up * speed * Time.deltaTime);
  
  if (Input.GetKey(KeyCode.LeftArrow))
     transform.Rotate(-Vector3.up * speed * Time.deltaTime);
  }
 }
 
 function OnMouseDown () {
     selectedId = GetInstanceID();
 }

That really is all there is to it, then...