widgets – modifying 'recent posts'

I’m pretty new to wordpress.org. Everything is running well. I know how to make simple themes, etc. However, I’m not where I want to go with this yet, and I’m not sure how to move forward. All the books I’ve previewed are roughly the same and the videos at Lynda.com were great at giving me the basics, but something from all that is missing that I want to know.

Please excuse me if I’m not speaking programmer-speak properly.

I went to find the ‘recent posts’ widget where I figured it would be: with all the other widgets/plugins. However, I could not find it.

I want to make a widget that works in conjunction with the ‘new post’ function either beside or beneath the New Post widget that comes with wordpress.org. In that widget would be all the images along with long (say 200 characters) descriptions per image that go with the post, but would be called in a separate box on the theme itself. On the theme, when viewed, I would have the main blog post appear in a given box along with text and basic images. On the right would be a smaller box with 3-5 images (with arrows should there be more images than what can fit) with the central image having the long description beneath it.

Would I have to modify the ‘new post’ function and the ‘new post’ widget in order to accomplish what I want? If so, where do I find these files to modify? Or should I just create an entirely new widget/plugin? Also, if you know of any tutorials or books that might help give me insight into how I would accomplish all this, I would appreciate it. The books I have found thus far don’t really deal with this kind of thing.

Thanks,
Steven