PHP simple question

I just downloaded a program that will let me post news on my site in an easy manner. The program is written in PHP. Right now my Index page is in .html extension. I was told that I should change the extension of the page to .php to make the program work.

There are quite a few sites that have linked to my homepage where the news is supposed to appear. Now if I change my index page from .html to .php will all the links be dead that are on all the sites or will they still work. Thanks a lot.