Definitely wouldn't try to capture the button click. Not only because that event won't bubble into GA by default, but because if it did work, you would register a conversion even if the lead didn't enter any valid data! (A submit button click doesn't == form submit.)
If you move the question to Products ("Central" is for general mktg questions, not product-specific ones) we'll continue there and I'll tell you where to track the conversion.
Hi Steve - did you ever find a solution? I didn't see you re-post to Products. I wish @SanfordWhiteman could have told you where to track the conversion when responding with his last post. I'm experiencing the same road block and looking for clarity