[thejeff]

The computer/connection is certainly sufficient.
The server does not have to be up 24/7. It only has to be up when players connect to it. It's generally easier to leave it up, since you don't know when players will want to connect.

1/2) That depends on you and your players. There's a timer and a quickhost option. The timer forces the game to host after a specified time, even if everyone has not played. Quickhost tells it to host as soon as everyone has. Games usually start with quickhost and a 24 hour timelimit. The first turns go quickly, then it slows down.

3) Not much. Try not to do it when someone is connected. You can restart the server without a problem. The timer will reset itself though. Not much point in having a 48-hour timer if your shutting down everyday.

4) Yes. Copy the game directory in savedgames. You can use the --postexec (or --preexec) option to do this automatically. There was some discussion about this around here quite awhile back.