I have had several of you ask how I was able to get my blog to 3 columns. I found this blog that gave step by step instructions on how to do it. Here is the link.
Bear in mind that your current background may not match up once you change it. If you need a new background there are LOTS of free ones out there. I googled in "Free 3 column blogger backgrounds" when I searched for mine. I was able to change my whole blog in less than 2 hours, it really is quite simple.
Email me if you are having any troubles figuring it out.