Definitely don't mind being asked questions. Feel free to ask!
As for the holster, I'm using a Safariland 013 competition holster (http://www.safariland.com/DutyGear/product.aspx?pid=013
) on a Safariland ELS rig. It works well for me.
The knob at the top of my gun is the brightness control for the C-more Serendipity Red-dot sight. The reddot takes up a lot of power so I turn it off when I'm not using it anymore.
hope that helps!