Ok. Here ya go

<script creator="Agent Moose" at="smcodes.smfforfree3.com">
var username = $('td.titlebg2 span b').not($("td.titlebg2 span b:contains(News)")).html()
if(username){
var name = "<b>"+username+"</b>"
}else{
var name = "<b>Guest</b>. Please Login or Register"
};
var News = "CONTENT"
$("#bodyarea").before('<div id="news_box"><div class="tborder" style="margin-top: 1ex;"><div class="catbg" style="padding: 5px 5px 5px 10px;">News</div><table id="upshrinkHeader2" width="100%" cellpadding="4" cellspacing="0" border="0"><tr><td class="windowbg"><span id="section">'+News+'</span></td></tr></table></div>');
</script>
Just like the Member/Guest Text, you can use "+name+" to show the users name, or if guest, Guest.
So, you could change the Content Part to this:
Welcome "+name+".
and it would come out this:
Welcome Agent Moose.