Resources to learn to use Powershell to automate IE functions

For the past several days I have been searching resources for how to use Powershell to automate IE functions.

We need to create powershell scripts to pass credentials into websites, to click on buttons on a webpage, to search for information and read it back into a powershell script, etc.

So far when I google Powershell IE automation, I only find few code examples, and I am struggling to get these examples to work.

My first question is, can you recommend good resources to learn and practice IE automation using powershell?

Second question is, I found code on technet, it looks correct, but I cannot understand why I'm getting so many errors:

$ie = new-object -com "InternetExplorer.Application"
$ie.visible = $true
$ie.navigate("http://www.gmail.com")
$doc = $ie.Document
$user = $doc.getElementByID("Email")
$user.value = "me@gmail.com"
$pass = $doc.getElementByID("Passwd")
$pass.value  = "my_password"
$Logon = $doc.getElementByID("signIn")
$Logon.click()

Please point me in the right direction.

EDIT:

Oh yes, and here are the errors

You cannot call a method on a null-valued expression.
At C:\sandbox\web2.ps1:10 char:28+ $user = $doc.getElementByID <<<< ("Email")+ CategoryInfo          : InvalidOperation: (getElementByID:String) [], RuntimeException+ FullyQualifiedErrorId : InvokeMethodOnNull
Property 'value' cannot be found on this object; make sure it exists and is settable.
At C:\sandbox\web2.ps1:12 char:7+ $user. <<<< value = "me@gmail.com"+ CategoryInfo          : InvalidOperation: (value:String) [], RuntimeException+ FullyQualifiedErrorId : PropertyNotFound
You cannot call a method on a null-valued expression.
At C:\sandbox\web2.ps1:14 char:28+ $pass = $doc.getElementByID <<<< ("Passwd")+ CategoryInfo          : InvalidOperation: (getElementByID:String) [], RuntimeException+ FullyQualifiedErrorId : InvokeMethodOnNull
Property 'value' cannot be found on this object; make sure it exists and is settable.
At C:\sandbox\web2.ps1:16 char:7+ $pass. <<<< value  = "my_password"+ CategoryInfo          : InvalidOperation: (value:String) [], RuntimeException+ FullyQualifiedErrorId : PropertyNotFound
You cannot call a method on a null-valued expression.
At C:\sandbox\web2.ps1:18 char:29+ $Logon = $doc.getElementByID <<<< ("signIn")+ CategoryInfo          : InvalidOperation: (getElementByID:String) [], RuntimeException+ FullyQualifiedErrorId : InvokeMethodOnNull
You cannot call a method on a null-valued expression.
At C:\sandbox\web2.ps1:20 char:13+ $Logon.click <<<< ()+ CategoryInfo          : InvalidOperation: (click:String) [], RuntimeException+ FullyQualifiedErrorId : InvokeMethodOnNull