Add clickable logo to TwentyTen theme using child theme

I would like to add a clickable logo to my twentyten-based site and am using a child theme to make changes (sounds good but I'm just starting out with child themes!).

Could anyone advise me how to do this - I've seen sites that say replace: -

 

<<?php echo $heading_tag; ?> id="site-title">
 <span>
 <a href="<?php echo home_url( '/' ); ?>" title="<?php echo  esc_attr( get_bloginfo( 'name', 'display' ) ); ?>"  rel="home"><?php bloginfo( 'name' ); ?></a>
 </span>
 </<?php echo $heading_tag; ?>>

Select all Open in new window

with

 

<h1 id="site-title">
<span>
<a href="<?php bloginfo ('home');?>" rel="home" title="<?php bloginfo('name');?>">
<img src="<?php echo bloginfo ('template_directory');?>/images/logo.png" alt="<?php bloginfo ('name');?>" />
</a>
</span>
</h1><!--end of h1 site-title-->

Select all Open in new window

Is this correct?

If so, I'm not sure: -

1. how do you remove the first segment using a child theme header.php file
2. how to include a link to make the logo clickable.

Help appreciated........