Customizing category pages

Hi,

I want to customize the Category pages on www.urbanbuiltllc.com (example: http://urbanbuiltllc.com/category/news/) in two ways, but not sure how to do either one as I'm not very fluent in php and I guess Wordpress no longer allows modifications to the loop through the Theme Options.

1. I want to display full-length posts as opposed to excerpts. Is it possible to display as many full-length posts as will fit in a set height? (So users could scroll down through posts as far as possible without, say, running past the background image.) If not, I would also be satisfied with picking a set number of posts to display.

2. I would also like "older posts" / "newer posts" links to display at the bottom of category pages. I found this code

<?php next_posts_link('Older Posts'); ?>
<?php previous_posts_link('Newer Posts'); ?>

but not sure where to add it.

Thanks!