There already is a Skype Me plug-in for Facebook.You set it up like this:
First, you log in to Facebook.
Once you do so you can access your Skype-connected Facebook accounts on this page:
After you've added specific Facebook friends to your SkypeMe, and you click on the green phone icon in your list of SkypeMe Facebook friends, you'll see a screen like this:
Then just click the green. If your friend has h/her Skype open, you should be conversing in seconds.