The template is /books_and_magazines/customer/tabs.tpl
You might want to watch my tutorial on webmaster mode if you are having trouble locating a template. The header is near the bottom of the template list for SEO reasons.
Consider this code for making it pull a language value:
Code:
{if $sb.title eq 'Home'}{$lng.lbl_site_path}{else}{$sb.title}{/if}
You can extend it by adding {elseif $sb.title eq 'Shopping Cart'} etc.