Pressnoob on "Amazon Product API plugin that retrieves the list price and the lowest price"

So I really want to make a plugin like this: http://www.convertazon.com/demo/ except without the cheesy loading bar and other stuff.

I'm just wondering if anyone has any experience creating Amazon product APIs and if you have any advice. I've never made a WP plugin myself.

This would go on top of the page:

<?php
    include("amazon_api_class.php");

    $obj = new AmazonProductAPI();

    try
    {
        $result = $obj->getItemByAsin(B0067HQL30);
    }
    catch(Exception $e)
    {
        echo $e->getMessage();
    }

function percent($Retail, $Low) {
$count1 = $Retail - $Low;
$count2 = $count1 / $Retail;
$count3 = $count2 * 100;
$count = number_format($count3, 2) . "%";
return $count;
}

$LowestP = $result->Items->Item->OfferSummary->LowestNewPrice->Amount;
$MSRP = $result->Items->Item->ItemAttributes->ListPrice->Amount;
$Savings =  $MSRP - $LowestP; 

$LowestP2 = number_format($LowestP /100,2);
$MSRP2 = number_format($MSRP /100,2);

?>

And this goes to the body of the page to style in however you'd like.

<h1> Percent: <?php echo percent($MSRP, $LowestP); ?> </h1>
<h2> Retail Price:$ <?php echo $MSRP2; ?> </h2>
<h1> Lowest Price:$ <?php echo $LowestP2; ?> </h1>
<h2> Total Savings:$ <?php echo number_format($Savings /100,2); ?> </h2>

There is only one real dynamic aspect of the plugin, the string of the function getItemByAsin. I guess you'd just retrieve the value from the WYSIWYG editor, is that it?