MythTV is more of a complete setup. It's not really the kind of thing you want to use just for watching movies you already, though MythVideo does this spectacularly well. The reason for this is that it is rather heavy on dependencies. It uses the MySQL database, the Apache web server and a load of other stuff. Myth is great, but you might do better with something like Freevo.
With lirc you can set a profile for individual applications so, for instance, you can set it up just with VLC to play, pause, stop, skip ahead, and skip back. This might be good for you. Be prepared to get your hands dirty with the CLI since this is probably the easiest way of setting it up.
If you choose to go with Myth, I recommend you start by installing the Mythbuntu control center with
sudo apt-get install mythbuntu-control-centre
since it pretty much automates setup after you've told it what role your system will play (frontend and backend in your case). The Myth wiki is great as well, containing info on a load of common and uncommon software along with guides.
I'vo got a MythTV thread going a few threads down. Feel free to ask questions in there.
