2000 CHEVROLET PRIZM Structurebodydoor Problems

AT 15K MILES, MY REAR PASSENGER WINDOW MOTOR QUIT WORKING. AT 35K MILES, MY DRIVER INDOOR "PLASTIC" DOOR HANDLE COMPLETELY BROKE OFF WITH NO WARNING WHATSOEVER. AT 75K MILES, MY DRIVER WINDOW MOTOR QUIT WORKING (I NOW HAVE NO WAY OF OPENING MY DOOR FROM THE INSIDE). AND AT 85K, MY PASSENGER FRONT DOOR HANDLE STARTED TO CRACK. THE DEALER WANTS TO CHARGE ALMOST $40 A PIECE FOR THE HANDLES, EACH, AND THEN 140.00 EACH TO INSTALL. THIS IS A LITTLE PIECE OF PLASTIC, AND SHOULD NOT BE SO MUCH. THE MOTORS ARE ROUGHLY $100 EACH TO REPLACE, PLUS THE LABOR. THE SEATBELT SIGN FLASHES ALL THE TIME, WHETHER I AM BUCKLED IN OR NOT, AND I AM TOLD THE WHOLE SEAT BELT NEEDS TO BE REPLACES, AT ANOTHER $235. NOW MY SPARK PLUG COILS ARE SUPPOSEDLY BAD, AND I AM LOOSING OIL. THE CAR HAS 82 MILES ON IT...