Hi and welcome.
If the "template" has only one layer with everything on it, then it's not what I'd call a real template. A proper template will have as many layers as it takes to break each element down for easy access.
On a single layer file, there isn't really a way to separate the lines from everything else in a quick, easy way. Redrawing each line is the primary option, and having done this many times, I know it takes a very long time!
What might help is try and locate some more refined templates. If searching doesn't turn up anything, you might put up a request post and see if anybody replies.