OK, I copied down the code and unzipped the style.css and uploaded that. That reverted it to the default, and the sidebar came back. Now I just have to go through and retweak the css again, hopefully not screwing it up this time.
OTHER QUESTION:
After I go through and retweak, I will probably once again face the issue of getting all of the sidebar showing the right background color. Can anybody help me out on that? Thanks.