harmonic balancer and broken door hinges

hi guys . well my dream century is turnin nightmare.first of all the serp belt started to fray.noticed balancer pully wobbling.asked shop to check it and they go ahead and change it . telling me to keep an eye on it .5 days later its fraying again. do i need a new balancer is the question? then the passenger door goes clunk and the hinge plate splits at the door.can this be welded without removeing door and will a weld hold these heavy doors?and oh ya a new balancer at dealer is BIG money is used a safe bet? :confused: :confused: