Just take out the screws. Swap the top out. Put the screws back in. It's that simple. It'll take longer to put a chip in.
Nonono, I mean a way to mod your current top to accomodate full-size DVDs without using those ugly Viper tops
You don't. If you want it to look decent you'll need either a new top or full case. If you don't care how it looks, play with the top off or cut your case apart to make it fit. Just get an Xecuter case. I have a translucent red case and it looks incredible.