You'll see the two category templates when viewing the main page with your categories. member.php there should be used for the link to the last poster, last member who uploaded, and the link to the username if the category is owned by a specific user. For the e-card template, that's used for the different layouts for e-cards and you can see them when previewing or viewing an e-card. As far as I can remember the only place member.php is used there is to link to the profile of the user who sent the card.
As far as I know vB
's built-in search and search/replace functions should work fine for something like this. I've never had a problem using those functions anyways.