Success Message upon form submit - two questions

Hi, I think this message has been asked before, but I have not been able to answer it using the resources I was able to find here. We are not PHP programmers (that's why we bought Form Builder) - so far the package works great - however we have this challenge:

#1 when users fill out the form, they submit it and then it defaults to another blank form. You can see the form here contact.html (Click on "email us" link at bottom of page) We would like to have a "message sent successfully" or something to that end displayed instead of a new, blank form.

If there are changes to the code please tell us exactly where it goes and what values we need to modify... (I know, we are php dummies...sorry)

Thanks !!
Mark