OK - I *think* this will help you.
To display HTML in a form for editing - you might want to convert the <br /> back into line breaks withing the text area.
$stext = str_replace("<br />","\n",$stext);
Then convert the " marks to "
$stext = str_replace(""",""",$stext);
Then I also believe you'll have to convert < and > so that they don't bust the form.
$stext = str_replace("<"","<",$stext);
$stext = str_replace(">"","&qt;",$stext);
I think that should do it.