Solved my own question with a little bit of trial and error, just following up for any future newbies like myself.
here's what I finally came up with:
iframe = window.document.getElementById("iframe");
iframedoc = iframe.contentDocument || iframe.contentWindow.document;
iframedoc.getElementById('gbqfq').value='Test';
that's a way to SET, can also use it to GET as well.
This definitely makes webscraping quite easy.
Thanks for such a great product!