wp-admin: overwrite html without changing core?

There are no good tutorials out there but you can start reading about add_filter and use the plugin adminimize.

You’ll probably know this but html is just a way of boxing items on a page in a semantic way. All the styling is done with css, you can just use “display: none” on items you don’t need.

Create a plugin or use the functions.php to add the custom css. You can also use jquery for changing html, for example, changing dropdown-boxes to radiobuttons etc. Put all of it in your theme.

There are no good guides or easy ways for this task.

Yes, but the problem is that i need to change the actual markup of the page, and that cant be done with only css :<

Then jquery is your solution.

And how would one go about doing that? Cant find any tutorials :<

add_action( 'admin_footer', 'catlist2radio' );
function catlist2radio(){
	echo '<script type="text/javascript">';
	echo 'jQuery("#typdiv .categorychecklist input, #argangdiv .categorychecklist input, #landdiv .categorychecklist input, #producentdiv .categorychecklist input")';
	echo '.each(function(){this.type="radio"});</script>';
}

For example: I use this code to change my custom taxonomies checkboxes to radiobuttons.