is template-functions.php editable?

I'm trying to get Marketpress up and running. I'm not really liking the order in which Marketpress is outputting the products info. I'd like to have the thumbnails first, then the title then the price. It's an easy fix if editing the template-functions.php file is doable.

But I absolutely do not want to edit this file if I'll need to remake those edits every upgrade. so basically I'm looking for input on; when I upgrade can I just swap the packaged template-functions.php with my custom one?