hey,
I'm also new to stock photography. I found it easier to get accepted bu shutterstock then Istock. I have 19 images in my shutterstock gallery and sold 19 in about a week and a half. I only have 4 in my istock gallery. They seem to reject everything i submit.
Anyways if you have problems just read the forums and do google searches. Although it is not the answer learning a few photoshop techniques defenatly wouldn't hurt. They help the newbie getting those images the way you would have wanted them to be in camera. Its no solution but it helps to get your pictures accepted while you learn to shoot better in camera.