With the amount of wordpress skins, tools and plugins available any knowledge of PHP or programming is not necessary at all. Of course some CSS knowledge will be handy as you can then edit the style sheet for the skin you decide to use. Even then I think you can have quite an advanced blog set up in wordpres without ever having to code or edit the css.
We are a
web design company in UK and we also maintain a blog offering web design, e commerce and search marketing resources for website owners so we do have the skills to code and modify our blog if required. However in the last few months since we have started to use wordpress we have never once had to edit the code.