FYI, blogger also has a "draft" blogger format. In it they are testing their new templates wizard, and if you use it to build/reformat your blog, it allows greater customization of columns, headers, background etc, without having to understand html or change your code.
go to draft.blogger.com. under the blog you want to change, choose "design". Before where it said "change template", there is now a template designer button.
I was able to use this to instantly make my columns wider just by dragging them.
Make sure to save a copy of your current blog code, in case you want to go back.