[Reformed Former Drupal User] How do I do conditional watermarking like TheDirty

I’m discovered the Flexible Upload plugin and it seems great so far, but what I’m going for is what TheDirty.com uses on their WP blog.

Question 1: How can I do this…?
If there is only one image in a post. It watermarks it.
If there is more than image in a post, it watermarks it with a different image (that says click for more photos).

Of course, I’ll design the image that has that (view more images) text on it, but how do I create this “if then else” behavior with two different watermarks?

Question 2: How do I fix this…?

The current behavior of my WP blog is that clicking an image opens the image separately in a window. I would rather it links to the entire post with comments.

Thanks in advance for the support, hopefully these questions weren’t too n00bish (the second probably is), but I’ll tell you, having used Drupal for a couple years, WordPress would have been the best solution for the types of blogging communities I’ve wanted to build. So, I’m glad to finally be a switcher ??