Ok, there are a few steps to complete:
1.) Open up archive.php and change this code (right at the top):
$k_option['custom']['bodyclass'] = ""; //<-- Display Sidebar
// $k_option['custom']['bodyclass'] = "fullwidth"; //<-- Dont display Sidebar
to this:
//$k_option['custom']['bodyclass'] = ""; //<-- Display Sidebar
$k_option['custom']['bodyclass'] = "fullwidth"; //<-- Dont display Sidebar
Make the same change in single.php.
Next, you can adjust the image size by changing this:
$preview_image = kriesi_post_thumb($post->ID, array('size'=> array('M'),
'display_link' => array('lightbox'), // '_prev_image_link' or array('lightbox')
'linkurl' => array ('fullscreen','_preview_big'),
'wh' => $k_option['custom']['imgSize']['M']
));
to this:
$preview_image = kriesi_post_thumb($post->ID, array('size'=> array('XL'),
'display_link' => array('lightbox'), // '_prev_image_link' or array('lightbox')
'linkurl' => array ('fullscreen','_preview_big'),
'wh' => $k_option['custom']['imgSize']['XL']
));
Make the same changes in single.php.
2.) To display the full post content, find and change this:
<?php the_excerpt() ?>
to this:
<?php the_content() ?>
3.) If you mean can you move one of the sidebars from the 2 column layout (as per the demo -> http://www.kriesi.at/themes/newscast/) to the left of the content, no you can't the sidebars are built into the same function. It is possible to modify the theme to add a separate sidebar - this is something I may put together in a tutorial if I get the time (no guarantees or timescale thought...).
Hope this helps!