function
Add-WebPartToPage($web, $page, $xmlReader, $zoneId, $zoneIndex, $marker)
{
    $wpManager = $web.GetLimitedWebPartManager($page.Url, [System.Web.UI.WebControls.WebParts.PersonalizationScope]::Shared);

    $errorMsg = "";
    $wpGuid = [System.Guid]::NewGuid().ToString();
    $wpKey = "g_" + $wpGuid.Replace("-","_");

    $wpInstance = $wpManager.ImportWebPart($xmlReader, [ref]$errorMsg);

    if([string]::IsNullOrEmpty($errorMsg))
    {
        $wpInstance.ID = $wpKey;
        $wpManager.AddWebPart($wpInstance, $zoneId, $zoneIndex);

        $oldContent = $page["WikiField"];
        $wpContent = '<div class="ms-rtestate-read ms-rte-wpbox" contenteditable="false"><div class="ms-rtestate-notify  ms-rtestate-read {0}" id="div_{0}" unselectable="on"></div><div id="vid_{0}" unselectable="on" style="display: none;"></div></div>' -f $wpGuid;
        $newContent = $oldContent.Replace($marker, $wpContent);
        $page["WikiField"] = $newContent;

        $page.Update();
    }
    else
    {
        Write-Host Error: $errorMsg;
    }
}

function
Delete-WebPartFromPage($web, $page, $wpName)
{
    $wpManager = $web.GetLimitedWebPartManager($page.Url, [System.Web.UI.WebControls.WebParts.PersonalizationScope]::Shared);
    $webParts = $wpManager.WebParts
    foreach($wp in $($webParts))
    {
        if ($wp.Title.StartsWith($wpName))
        {
            $wpManager.DeleteWebPart($wp);
        }
    }
}