Where is my logic wrong???

I know this is long, but i would really appreciate some help from someone who understands wordpress well. any pointers at all would really be appreciated.
thank u

I want to incorporate a completely unique horizontal-scrolling theme for just one particular category in my vertical scrolling blog i have now.
This new horizontal-scrolling theme is good to go by itself (i tested it out and it works). it contains an index.php, .css, header.php, and footer.php.

this is what i have done so far:
1) changed index.php to category-3.php (3 being the id for the category i want the theme to work for) and changed the get_header part to <?php get_header(‘myheader’);?> so as it won’t grab my current theme’s header

2) changed header.php to header-myheader.php

3) changed the .css page to mystyle.css so it won’t interfere with my current themes .css sheet.

4) changed code where the now header-myheader.php grabs the css to <link rel=”stylesheet” type=”text/css” href=”contains url to mystyle.css here” />

4) i left the footer out figuring this new category can use the current footer.php

what it looks like is vertical still and just looks messed up.

thank you if you can help at all!