Merging categories, archives and single pages

Hi there,

these may very well be the ultimate noob questions, but here I go. 🙂

How can I make the single page template the standard template for ALL pages?
OR: How can I add previous_post_link to category pages?

See, I’m using the “view one post per page” setting for my blog, which sadly gives me *three* different pages per post, which all feature different functionality. I’d like to merge these three into one, since I don’t need to differentiate between archives and categories, and I don’t need to differentiate between “one post per page” views in my cats and the “real” single page view. I also don’t need to differentiate between index.php (or “blog home”) and the latest post in the main category.

So…

• I’d like to have a certain category (news) to always be the front page (index.php).
• I’d like to have the main content display the latest post in the current category.
• I’d like to have previous_post_link and next_post_link on *every* page.
• I’d like to have the sidebar with a simple category listing; current category highlighted.
• I’d like to have “comments_popup_link” below a post, taking the user to the item’s page with the comments and the comments field.

I wonder how to achieve this. Some of these things seem to be reserved for “single.php”, while others seem to be reserved for “index.php”, and yet again others seem to take categories and archives into account.

The site I’m working on is Stanis Erben. Please view with standards compliant browser, as IE currently mixes it up real bad.

As you might see, the menu to the right should simply switch to the newest post in each category. This works, of course, but I’m unable to use previous_post_link on the resulting page, as it’s a category page which only allows previous_posts_link — a bummer, really.
Also, I’m using the catHighlight plugin. This, oddly enough, only works on cat-pages and not on single pages, making it virtually useless for my needs.

Am I making sense? 🙂

Any help highly appreciated.
So much, in fact, that I’ll gladly give credit on the page.

Thanks in advance.
Marcus