As it turns out, I went to the bridge district to do what anomen's father wanted and anomen goes berserk and kills the guy in the palace's daughter...and many hours later I find out that Anomen can't complete his knight quest because of this. Ooops! And...he failed. I look at him and he doesn't really look that great. Who should I replace him with? And...who is a good thief?

Aramar

the replacement depends on who the rest of your party are

a good theif can be found in the goverment district: Jan Jansen

If your party is mostly neutral/evil, I'd hire Viconia.

If your party has one or two good characters in it but your personal charisma is high and you keep your rep in the midrange, you should still be able to hire Viconia without any hassles. (But if your rep rises too high or your charisma is low, fights may break out.)

If you prefer a neutral/good party, consider Jaheira. Although she lacks the high level anti-Undead spells of clerics, being a Harper means she gets the Raise Dead spell, which Cernd lacks.

Alternatively, reload an earlier saved game, and give Anomen different advice that will allow him to keep his dad's killer alive. ;)

thief : dont take Nalia , she sucks

take jan jansen or yohsimo