Confused by Code

I really wanted to make my Blog prettier, but only succeeded in making it really ugly. I guess i don't understand code, and I'm having problems figuring where stuff is in the code. For Example, how do I change the side bar color, and how do I get rid of the background image in the top of my template. I have sort of just been making random changes and experimenting. Also, where can I add an image in the side bar. I used the help section on Blogger, but obviously it was written by a programming geek who thinks we are all HTML code literate. I bet he looks like this.