Help converting a script to a snippet

<?php 
	require("clients/dbconnect.php");

	if ($_SESSION['uid'])
	{
	    	$query="SELECT * FROM tblclients WHERE id='" .sanitize($_SESSION['uid']) . "'";
		$result = mysql_query($query) or die(mysql_error());
		if($row = mysql_fetch_array($result, MYSQL_ASSOC)) 
		{
			$clientsdetails['firstname']=$row['firstname'];
			$clientsdetails['lastname']=$row['lastname'];
			$clientsdetails['email']=$row['email'];
		}
		echo "Welcome Back, <strong>".($row['firstname'])."</strong>   <img src=\"/clients/templates/portal/images/icons/details.gif\" alt=\"My Details\" width=\"16\" height=\"16\" border=\"0\" class=\"absmiddle\" /> <a href=\"/clients/clientarea.php?action=details\" title=\"My Details\"><strong>My Details</strong></a>   <img src=\"/clients/templates/portal/images/icons/logout.gif\" alt=\"Logout\" width=\"16\" height=\"16\" border=\"0\" class=\"absmiddle\" /> <a href=\"/clients/logout.php\" title=\"Logout\"><strong>Logout</strong></a>";
	}
	else
	{
		echo "Please <a href=\"/clients/clientarea.php\" title=\"Login\"><strong>Login</strong></a> or <a href=\"/clients/register.php\" title=\"Register\"><strong>Register</strong></a>";
	}
?>

<?php
$output = "";
/* some code */

$output .= 'Some HTML';

/* some more code */

$output .= 'Some more HTML';


return $output;

--Template HTML--
If logged in to WHMCS, then show: Welcome back User.
Else: Log in to access client area.
--Template HTML header--
--Template HTML main menu--
If logged in to WHMCS, then show: WHMCS Client Menu.
Else: Show nothing
--Template HTML the rest--

[[MySnippet? &LoggedIn=`1` &Stop=`0`]] Insert my Template text inside here[[MySnippet? &Stop=`1`]]

<?php

$loggedIn = // Your code here to check login status

if (! $loggedIn) {
    $modx->sendRedirect('Full/URL/of/Login/page');
}

return "Welcome Back, <strong>".($row['firstname'])."</strong>   <img src=\"/clients/templates/portal/images/icons/details.gif\" alt=\"My Details\" width=\"16\" height=\"16\" border=\"0\" class=\"absmiddle\" /> <a href=\"/clients/clientarea.php?action=details\" title=\"My Details\"><strong>My Details</strong></a>   <img src=\"/clients/templates/portal/images/icons/logout.gif\" alt=\"Logout\" width=\"16\" height=\"16\" border=\"0\" class=\"absmiddle\" /> <a href=\"/clients/logout.php\" title=\"Logout\"><strong>Logout</strong></a>";