Sharepoint Services on Existing web server

Hi, We are in need of a out of the box Intranet and Document Repository, which I feel Sharepoint services would be the best option. We currently have a web server running IIS with quite a few default web sites running on it.

I want to install WSS so I can slowly build up the intranet functions and document repositry, but have read from a few places that it can ‘screw’ up existing sites.

Our sites our business crital so do not want to come across problems.

Has anyone got any advice??

Our web server ‘Windows Server 2003 R2’, IIS 6, SQL on a different server..

Thanks

Jay