Unfortunatly, my setup and what you have in mind don't have that much in common. My systems are all identical and pre-configured with each game using a unique CD-Key. One of the things you will need to set up in advance is how legal you want to keep things. The less legal the smoother things will go.
Example 1 (hard-ass):
Require that each computer already have the full compliment of games already patched to the latest before it arrives, and already be configured for DHCP. Provide a "minimum" and "recomended" hardware config so people know what to expect. This will give you a great gaming experience, but may keep a bunch of people away.
Example 2 (pirate):
Have a file server already set up containing the latest version of Daemon Tools and all the ISO images of all the games. If you really want to push it, have a folder full of keygen apps sitting out there as well. Everyone will be able to play all the games with minimal effort; and with a little luck you can avoid jail time.
Any compromise on either will cause complications, up to you.
Regarding promotion: Word of mouth, assisted by flyers, is the be-all and end-all of this market. Find people that know people and "hook them up" (free entry probably) to be your promoters. Get 4 people to bring 10 people each, a clan of sorts, and start the competition there.
Regarding games: Call of Duty works really well for this sort of thing. Rainbox6 is too slow, and the Battlefield games still prefer more players (50-64) before it gets really exciting. Doom3 is a lot of fun, but multiplayer is limited to 4 per server (lame). Warcraft 3 seems to be the most popular RTS at the moment (CNC: Generals would be, but it's unstable).
Too tired, might post more later. Any particular questions?