If you want to play the video on your own html page, you can do this.
<iframe width="420" height="345"
src="http://www.youtube.com/embed/SPbBdqqcsFY">
</iframe>
or
<embed
width="420" height="345"
src="http://www.youtube.com/v/SPbBdqqcsFY"
type="application/x-shockwave-flash">
</embed>
Overlay i would suggest that you made a Jquery like:
<div id="overlay">Click to watch video</div>
$("#overlay").click(function () {
$(this).html(your stuff goes here)
});