If you kill me, then you'll have to load your last save, which was like two hours ago.
It drives me CRAZY though that you can't kill Maven. After you finish the Civil War, you can hunt down and kill the formerly-immortal Legates, but even after clearing the Thieve's Guild quests, Maven remains immortal?
Farengar Secret-Fire ish one of the firsht magesh that you meet in all of Shkyrim. He ish the Jarl of Whiterun'sh aid.