how to modify a server?

[Justinld]

Hey, my friend has a server and wants to make a few modifications, if anyone could say how to do them it would be cool. First, is there a way to prevent /kill so people cant commit suicide? If not, is there a command to have a long respawn time for self killers? Also, can you transfer effects of rage to after respawn(i know this is probably impossible). I mean, can you keep the regen time for after rage untill the time has completely worn off? Thanks to anyone that knows how to do any of this.