I am wondering if this keeps a post as the very first post on your page all the time? Or does it do something else?
I agree with hmansfield, you do not need a plugin to do that, just look at publish box, and look for sticky option. If we can do that manually, why would we need a plugin? since plugin slows down your site, and some aren't developed.
Yes, the post will move down, unless you do some code tweaks. The easiest will just put the post set to "sticky" then it will stay on the top of your home page. To achieve this, you can easily set it in your dashboard, we don't need a plugin. Check my site, i have created a tut some weeks ago. Good luck.