Customizing Suffusion header and background

I have spent a couple of nights trying to customize the Suffusion theme to my liking, but so far it seems that I’m too daft to understand the explanations I’ve found. So if anyone in very simple words and step-by-step could explain to me how to do the two following things I would be extremely grateful.

1) How do I insert my own logo in the header. It seem that I have to point to a url to do so, can’t I upload one from my computer? I would also like to expand the height to 200 px.

2) In the default design, the area around the posts and widgets are light grey. I would like it to be white. How do I go about to achieve this?

I have been to the Aquoide Forum without being any wiser, so a reference to that page will unfortunately not help me.