When I try to access the stats directory of my domain, it asks for authentication. I tried my FTP credentials and my panel login, but neither works. Where can I change/add users for the stats directory?
From the Control Panel -> Status -> Site Statistics screen. Just click the linked number under the "Stats Users" adjacent for the domain in question; the following screen will give you what you need.
Oh my gosh. I'm an idiot.
Ha! I don't think so - that is not a very intuitive place to put that, IMO.