Running ASP.net and PHP websites

I am running an ASP.net website on a dedicated server and I now want to install PHP to run Wordpress.

1. If I use the Web Installer on the web server to setup the PHP site, will it mess up the existing ASP.net sites?
2. Is it 'safe' to have the ASP.net and PHP sites running in parallel?
3. Is is possible to have the sites running in parallel with just a single external IP? (Does iis redirect the IP to the correct ASP.net or PHP instance?)

Thanks for your help.