I finally found how to do it in a simple way :-) Here we go ...
(I assume you know how to ovewrite a theme file and to display a view using the Table styling)
1- Enable the pagination (without this you won't get the $view->total_rows value)
2- Copy and the file 'views-view-table.tpl.php' in your theme folder (themes/garland or sites/all/themes/my_theme for example)3- Rebuild the theme registry to enable your new table_theme file
4- Adding the total by displaying the $view->total_rows variable
TOTAL : total_rows ; ?>
and that's it !!PS: As far as the line number counter all you need is to define a variable ($counter) that you increment in the foreach loop.