ryanfitzer, I don't think the OP wants to add or subtract content from a sidebar, they physically want to add or subtract the sidebar column.
Which is, IMO, far and beyond the scope of a WP support forum post, which, IS, from what I can gather, what the OP wants.
The answer is more CSS based than WP. The issue is about how the page is displayed, relative to widths, either in pixels or %, and the overall width of the page. It's not as simple as adding an additional PHP include to add another file worth of content. You must really dissect the style sheet and determine what and where you can add another column, THEN, you could do a
<?php include 'sidebar2.php'; ?> to add your additional content.
Since you don't want links, I won't bother adding any to CSS references I would suggest.
I'll add that deleting content might be easier, bu t the display could just as easily be borked by doing so, depending on the theme.