when i click links in the sidebar, they open both in the sidebar and in my main firefox window, any way around this problem that you know of? like when i click to view a gmail message, i want to read that message in the sidebar, but it loads in both the sidebar and the main firefox window.

Try holding down the Control key while clicking on a link, or try middle-clicking on a link. I believe that will force them to open in a new tab.