How to convert to 2D

The script below is one for a 3d Object but I need its functionality, but I'm having trouble converting it so that I can use it in Unity's new 2d platform with the 2d colliders and rigidbodies this script is made for the default rigid bodies and colliders? Can anyone help!

  var normalCollisionCount = 1;
 var moveLimit = .5;
 var collisionMoveFactor = .01;
 var addHeightWhenClicked = 0.0;
 var freezeRotationOnDrag = true;
 var cam : Camera;
 private var myRigidbody : Rigidbody;
 private var myTransform : Transform;
 private var canMove = false;
 private var yPos : float;
 private var gravitySetting : boolean;
 private var freezeRotationSetting : boolean;
 private var sqrMoveLimit : float;
 private var collisionCount = 0;
 private var camTransform : Transform;
  
 function Start () {
     myRigidbody = rigidbody;
     myTransform = transform;
     if (!cam) {
         cam = Camera.main;
     }
     if (!cam) {
         Debug.LogError("Can't find camera tagged MainCamera");
         return;
     }
     camTransform = cam.transform;
     sqrMoveLimit = moveLimit * moveLimit;    // Since we're using sqrMagnitude, which is faster than magnitude
 }
  
 function OnMouseDown () {
     canMove = true;
     myTransform.Translate(Vector3.up*addHeightWhenClicked);
     gravitySetting = myRigidbody.useGravity;
     freezeRotationSetting = myRigidbody.freezeRotation;
     myRigidbody.useGravity = false;
     myRigidbody.freezeRotation = freezeRotationOnDrag;
     yPos = myTransform.position.y;
 }
  
 function OnMouseUp () {
     canMove = false;
     myRigidbody.useGravity = gravitySetting;
     myRigidbody.freezeRotation = freezeRotationSetting;
     if (!myRigidbody.useGravity) {
         myTransform.position.y = yPos-addHeightWhenClicked;
     }
 }
  
 function OnCollisionEnter () {
     collisionCount++;
 }
  
 function OnCollisionExit () {
     collisionCount--;
 }
  
 function FixedUpdate () {
     if (!canMove) return;
  
     myRigidbody.velocity = Vector3.zero;
     myRigidbody.angularVelocity = Vector3.zero;
     myTransform.position.y = yPos;
     var mousePos = Input.mousePosition;
     var move = cam.ScreenToWorldPoint(Vector3(mousePos.x, mousePos.y, camTransform.position.y - myTransform.position.y)) - myTransform.position;
     move.y = 0.0;
     if (collisionCount > normalCollisionCount) {
         move = move.normalized*collisionMoveFactor;
     }
     else if (move.sqrMagnitude > sqrMoveLimit) {
         move = move.normalized*moveLimit;
     }
  
     myRigidbody.MovePosition(myRigidbody.position + move);
 }
  
 @script RequireComponent(Rigidbody)