Script Errors when nothing wrong...I think

Ok, I am a beginner, so it could likely be something I’m doing wrong, but I don’t think so. I put the below script in Unity before and it worked, but now as I was editing stuff at the bottom (the About Game guiMode and the How to Play guiMode), it gave me these errors:

(17, 20 [ if(guiMode = “Main”) ] ) - BCE0044: expecting ), found ‘=’).

(17 22) - BCE0043: Unexpected token: Main.

(20, 17 [ just under //New Game Button ] ) - BCD0043: Unexpected token: if.

(20, 119) UCE0001: ‘;’ expected. Insert a semicolon at the end.

(22, 61 [ PlayerPrefs.GetInt…] ) BCE0044: expecting :, found ‘;’.

#pragma strict
@script ExecuteInEditMode()

var myGUI : GUISkin;
var buttonWidth : float;
var guiMode : string = "Main";

function Start()
{
	guiMode = "Main";
}

function OnGUI()
{
	GUI.skin = myGUI;
	
	if(guiMode = "Main")
	{
		// New Game
		if(GUI.Button(Rect (Screen.width/2-(buttonWidth/2), Screen.height/2-20, buttonWidth, 30), "New Game"))
		{
			PlayerPrefs.GetInt("playerLevel", 1);
			Debug.Log("New Game Clicked");
			Application.LoadLevel(1);
		}
		
		// Continue Game
		if(PlayerPrefs.HasKey("playerLevel"))
		{
			if(GUI.Button(Rect (Screen.width/2-(buttonWidth/2), Screen.height/2+20, buttonWidth, 30), "Continue Game"))
			{
				Application.LoadLevel(PlayerPrefs.GetInt("playerLevel"));
			}
		}
		else
		{
			GUI.Box(Rect (Screen.width/2-(buttonWidth/2), Screen.height/2+20, buttonWidth, 30), "Continue Game");
		}
		
		//How to Play
		if(GUI.Button(Rect (Screen.width/2-(buttonWidth/2), Screen.height/2+60, buttonWidth, 30), "How to Play"))
		{
			guiMode = "HowTo";
		}
		
		//About Game
		if(GUI.Button(Rect (Screen.width/2-(buttonWidth/2), Screen.height/2+100, buttonWidth, 30), "About Game"))
		{
			guiMode = "About";
		}
	}
	
	if(guiMode = "HowTo")
	{
		Debug.Log("How to Play");
	
		//Back to Main Menu 
		if(GUI.Button(Rect (Screen.width/2-(buttonWidth/2), Screen.height/2+100, buttonWidth, 30), "About Game"))
		{
			Debug.Log("About Clicked");
		}
	}
	
	if(guiMode = "About")
	{
		Debug.Log("About Game");
		
		//Back to Main Menu 
		if(GUI.Button(Rect (Screen.width/2-(buttonWidth/2), Screen.height/2+100, buttonWidth, 30), "About Game"))
		{
			Debug.Log("About Clicked");
		}
	}
}

What am I doing wrong?

start with line 17 : your conditional only has one equals sign, it needs to say “is equal to” ==

if ( something == somethingElse ) 

if ( guiMode == "Main" )

the same goes for all your conditionals. Check the list of operators on this link : http://forum.unity3d.com/threads/173876-Programming-and-Making-Games-with-Unity-3D