I am presently using Apache+Phusion quite effectively but am thinking about testing out nginx+phusion. Although you will find plenty of places where I'm able to get info regarding how to setup the second not one of them explain what I must do to make sure that it's nginx that's serving some misconception instead of Apache.

Ideally I must keep your Apache stuff available although trialling but I am speculating that at least I will need to stop Apache and run nginx..... or can both be running concurrently on a single machine? When the response to this really is yes then which server will handle url demands and just how am i going to know?