equilibriumx
With SEO, you can make some research as there will be many references discussing about this. I can help you with template matter only.
If you want to change h4 to a div tag, you open above file:
<?php if ($this->API->get('logo_type', 'image')!=='none'): ?>
<?php if($this->API->get('logo_type', 'image') == 'css') : ?>
<h4 class="gkLogo">
<a href="<?php echo JURI::root(); ?>" id="gkLogo" class="cssLogo"><?php echo $this->API->get('logo_text', ''); ?></a>
</h4>
<?php elseif($this->API->get('logo_type', 'image')=='text') : ?>
<h4 class="gkLogo">
<a href="<?php echo JURI::root(); ?>" id="gkLogo" class="text">
<span><?php echo preg_replace('/__(.*?)__/i', '<span>${1}</span>', $this->API->get('logo_text', '')); ?></span>
<?php if($this->API->get('logo_slogan', '') != '') : ?>
<small class="gkLogoSlogan"><?php echo $this->API->get('logo_slogan', ''); ?></small>
<?php endif; ?>
</a>
</h4>
<?php elseif($this->API->get('logo_type', 'image')=='image') : ?>
<h4 class="gkLogo">
<a href="<?php echo JURI::root(); ?>" id="gkLogo">
<img src="<?php echo $logo_image; ?>" alt="<?php echo $this->API->getPageName(); ?>" />
</a>
</h4>
<?php endif; ?>
<?php endif; ?>
You will see snippet of code like this:
<h4 class="gkLogo">
<a href="<?php echo JURI::root(); ?>" id="gkLogo">
<img src="<?php echo $logo_image; ?>" alt="<?php echo $this->API->getPageName(); ?>" />
</a>
</h4>
change it to:
<div class="gkLogo">
<a href="<?php echo JURI::root(); ?>" id="gkLogo">
<img src="<?php echo $logo_image; ?>" alt="<?php echo $this->API->getPageName(); ?>" />
</a>
</div>