.htaccess mod_rewrite ..and trying to avoid making template changes

I’m currently using the Skyfashion theme on the latest install of WP, and my biggest concern is that if/when the theme gets updated, any changes I make to the internal workings will disappear with each release. And it’s not something I particularly want to do more than I have to.

What I’m attempting to do at the moment regards the common ‘Portfolio’ (extension?) and the slugs contained therein. By default, these are /skills for categories, and /portfolio for individual entries.

Given that neither of these physically exist, I’m not sure how one would go about doing a rewrite, but what I’m trying to achieve is to make

domain.is/skills

be displayed as

domain.is/shooting

So if you click on the first link, it will DISPLAY as (not redirect to!) the second. It’s important that this is done superficially, as the theme will continue to LINK to /skills – I just want it to DISPLAY as something different.

My WP install is in /wp/ but I have everything operating out of the root directory (which is where the htaccess file is located).

Any help would be greatly appreciated.