I am adding another answer, as I have recently had to do this and managed to do it without modifying data in the theme layer.
You can add a preprocess function to your view. It is a bit of work though.
There are some guidelines here, but they are a bit confusing. Here is my summary of how to do this.
First make sure your modules weight is > views
Secondly copy the template you would like to add a preprocessor to to your modules directory. Rename it to be something in the list of templates in theming information.
Then edit hook theme like this (but change to use the existing view that you need to override.
function mymodule_theme($existing, $type, $theme, $path) {
// Copy the exsisting views theme from the existing array.
$override = $existing['views_view_row_rss'];
// Add my preprocessor to the list of preprocess functions
$override['preprocess functions'][] = 'mymodule_myfunction';
// Point to a template so that this view will be used.
$override['template'] = 'my_more_specific_template_name';
$override['path'] = drupal_get_path('module', 'path');
unset($override['file']);
// Return your theme handler.
return array('my_more_specific_template_name' => $override);
}
You should then be able to write your preprocess code in the function mymodule_myfunction.