Left my 2006 BMW 325i Convertible out in heavy rain. When i got in, reversing i got a jerk, then drive errors. Took it to a shop and computer read faulty ignition coils. on closer insection thats when we realised there was still water draining out of the box. we attempted to dry it out now the car wont start. Do i need a new box and will i need to but that only or set including keys and CAS unit?