Ok, the online now thing is in each post. If you look in the bottom left of each post, you'll see something that looks like a V (the vBulletin symbol, at least for the default blue theme). If it is white, then the user is online, if it is dark, then the user is offline or hidden.
Now then, for each and every user, you can simply click their username in the post and it will bring up a small but useful menu where you can PM the user, view their profile, etc. For those with a colored and bold name, you should automatically recognize that the member is part of the staff. It's simple to remember the colors too. So, I think this takes care of it