I had already found the WP Video Lightbox Plugin, which is very easy to use (but not available here on WP) but thought I'd try this one because it is available here on WP.
Did everything described in installation and FAQs, but couldn't get more than the image itself (with code visible) to display.
WP Video Lightbox Plugin:
One plugin to install
Uses regular WP media upload
Insert shortcode in page or post
Add Youtube video id and image link to shortcode
"voila, one video!"