Is it possible to switch to Nginx?

I have Apache on my Virtualmin server (which currently runs PHP/MySQL sites). However I am launching a Rails site soon, and a popular set-up in the Rails community seems to be Nginx and Unicorn - hence wondered if if could switch over to Nginx to run all of the sites on the server.

The Nginx info page here says it must be installed after a clean install, but my server's a few months old now - are there any other options for me? If anyone's running Rails apps on a Virtualmin server - what do you use?

Thanks in advance.