I don't know about setting up send mail but the sending of an email is very easy.
at the very least try
mail($mailto,$subject,$body,"From:me@webbox.com");
I use a tool call quikmail for anything more than the most basic email. quikmail is probably here but the writer also quotes http://paulschreiber.com
Only use php if it's going to add value to your email. Have you tried just having this on your form:
form name="mail_form" action="mailto:me@webbox.com?Subject=Sent from the web" method="POST" enctype="text/plain">
gives an acceptable plain text format. You have field names so this may not be what you need.
good luck