Blog Help....

So....I need some "blog help". I want to redo my blog...change some backgrounds and colors and such...as I have noticed some other blogs and they look great....but I am not that quick at things like this....my sister even had to set this blog up for me!!! So can anyone tell me the fastest and easiest way to do changes to this blog and a good place where I can get some cool backgrounds and so forth....thanks heaps!!!