dfsn, dfsr and regular file system

I have a 2008 r2 DC primary and two backup 2003 server dcs.

I wuld like to setup dfsn for the main point of using dfsr between two
member servers a two different sites. My questions are:

1. does setting up dfsn in anyway affect are current file sharing setup?
Currently we use a file server to share files to clients through standard
shares ntfs folders.

2. Can this system coexist with a dfsn system?

3. Can I have just dfsr without using dfsn?