Hi,
The thank you message is displayed by the file end.php of the view "checkout". You can edit it via the menu Display>Views.
There, you'll see this code:
echo JText::_('THANK_YOU_FOR_PURCHASE');
if(!empty($this->url))
echo '<br/>'.JText::sprintf('YOU_CAN_NOW_ACCESS_YOUR_ORDER_HERE', $this->url);
which displays the standard thank you message.
So you can edit the code there.
If you want to redirect the customer to the order page, then you could do a redirect on $this->url.
For example:
$app = JFactory::getApplication();
$app->redirect($this->url);
Regarding the CSS, you could directly add HTML tags with CSS inline or classes of your own in there as you need.
Regarding the PayPal redirection area, it's displayed by the file plugins/hikashoppayment/paypal/paypal_end.php^
If you look at that file, you can see this code:
<span id="hikashop_paypal_end_message" class="hikashop_paypal_end_message">
<?php echo JText::sprintf('PLEASE_WAIT_BEFORE_REDIRECTION_TO_X', $this->payment_name).'<br/><span id="hikashop_paypal_button_message">'. JText::_('CLICK_ON_BUTTON_IF_NOT_REDIRECTED').'</span>';?>
</span>
So with CSS, you can just use the classes already available to customize the look.
For example, you could add such CSS to change the color of the text to red:
#hikashop_paypal_end_message{ color: red !important; }
www.hikashop.com/support/documentation/1...ize-the-display.html