If it's not to serious than maybe confronting the person will be okay. If it's serious like harassment, if they are stealing or something like that then I would got to the employer because you probably wouldn't be able to reason with them anyway. Also, if you offend the person and they feel that their job is in jeopardy then they may try to turn the tables on you. You really just have to decide ba<x>sed on the type of problem and the type of person that the problem is with.
Face to face. Acting scaired only atracts weak idiots to mess with you
Depends on what kind of conflict if its major then you should probably talk to the manager.