Questions About Rooting and Un-Rooting a Kindle Fire HD

I have a Kindle Fire HD and would like to install a SwiftKey keyboard on it. I am told that this is possible
but in order to accomplish this I need to 'root' the device. And once installed I can unroot the device again.
Is this possible? How easy and safe is it, and where can I get instructions/tutorials on how to do this?

Thanks for any feedback I can get on this.

Nothing I can find on their Play page or their site that says that the device has to be rooted too install the keyboard. Just install the trial and see if you like it. If you like it enough to pay for it, pay and get the full use.

As with any app, if you don't like it you can uninstall it.