Replacing submit button with text?

you can use an anchor tag with javascript to trigger the form change. e.g.

<form id="myForm" ...>
  ...
  <a href="#" onclick="document.getElementById('myForm').submit();">Submit</a>
</form>

You could also use almost any textual tag, by the way, just binding to the onclick event (a <span> for instance).

No, you need to use a different HTML entity (i.e, just a link).

But, I'd recommend you don't change it. It's better, from a user experience point of view, to use the typical submit buttons, perhaps styled slightly if appropriate, but nevertheless remaining as close to 'typical' as possible.

The reasoning is that OS' display the button in different (and familiar) ways to the user, and it's good UI design practice to follow "standards". This iy just my humble opinion.

Technically, you can quite easily make a link do the form submission, by setting the onclick event to something appropriate (like: onclick="return doFormSubmit();").