First, you need to have a PSN account. Then, when you have your internet cable attached and you load the game, you need to go to multiplayer and pick 'Player Match.' It should automatically log you...
If you are looking for the hidden computer behind the chair at the main menu, the code is "DOA" I think. You could also type "zork" and play the real text based game.
$60 new from retailers like walmart, target, etc. I beliee gamestop has it used for $50 though. In my opinion, it is worth it to spend the little extra money to get your own brand new copy, as used...