You just need to determine what's content and what's "structure" (bg, header, nav, images you want to keep on every page, section divs,footer, and the like). How easily you can do this depends on what was used to build the template and what you're savy in. I'm a novice bare-bones notepad html and php coder, so if someone built the template with .asp, filled the whole thing with js, or used DOM object orientated code, I'd have a tough time with it.