Migrate Apache+Phusion to Nginx+Phusion

I'm currently using Apache+Phusion quite successfully but am interested in trying out Nginx+Phusion. Although there are lots of places where I can get info on how to set up the latter none of them explain what I have to do to ensure that it is Nginx that is serving things up rather than Apache.

Ideally I would like to keep the Apache stuff available whilst trialling but I'm guessing that at a minimum I will have to stop Apache and开发者_如何学C run Nginx - or can both be running simultaneously on the same machine? If the answer to this is yes then which server will handle URL requests and how will I know?