Well, you did a decent job, but there were parts that you really should have worked on more.
For one, your renderings were pretty poor, and the only excuse for that is a lack of practice or patience. Using the path tool, all you need is about an hour and a good eye, and it's really not that tough. But hey, you've only been doing this one year, give it some time and you'll improve.
The second problem is the the sharpness; the transitions from colored to monochrome are all really pixelated lines, which looks absolutely horrid. On top of that, the second character from the left is extremely blurry, which is the fault of either a bad picture you cut from, or a bad resizing job. Either way, you need to sharpen that.
Now, while those first two are maybe understandable, innocent mistakes, this next one isn't. On the bottom right of the post, just below the text, it's obvious that you tried to cut away the colored bar with a circle eraser tool. Honestly, that's inexcusable and extremely lazy, not to mention you did a really bad job. Next time, try using the Path tool to cut it away.
On top of that, your "In Theaters March 2008" text looks shoddy, and not evenly planed; your text is also not italic, like it is in the real poster, but the texturing is good.
Overall, a decent try, but you need some work on execution.