Adds Icons after links according to whether you've specified XFN or not.
Yes. Yes it is. That's all that is needed. Everything else is already implemented in WordPress by default.
Yes. It is too simple not to.
The PHP calls for a simple stylesheet to be added to the main page. All that is in this stylesheet is markup for icons to be added after the links. Nothing else.
Refresh you page, and perhaps clear your cache and refresh again. Don't worry, even I fell into this trap.