Joomla 1.5 - Customize Section and Category pages

I'm building a website in Joomla 1.5, and I need some help. I've attached "[login to view URL]" to help me describe how I want the site built. I am going to have a whole bunch of articles (not all the articles, but most of them), and for each of these articles I want to be able to associate a thumbnail picture with each one, as well as some text. And then, I'm going to have pages that represent my categories, so all the articles in that category, will be represented by their thumbnail and text. The user can also click on those thumbnails or text in order to get to that article. The categories themselves will have their own thumbnail and text. And then I'll have pages that represent sections, so the categories in that section will be represented by the category's thumbnail. And then the user can click on those thumbnails (and text) in order to get to the category page. The purpose of the site being setup like this is so whenever my client wants to add a new article, the category and section pages will update automatically! Also when you build this site, I will also need you to apply tags (eg. <div> <a class="&#133;) so I'm able to style everything with CSS. I'll take care of the css, templates etc. I only want to pay a one-off fee, do not use an extension, module or plugin that requires a monthly subscription/payment.