burned wires in converter. Fix wires or replace converter?

That looks to be a piece of phenolic (ie a piece of circuit board with no components on it) used to insulate the neutral buss from the chassis ground. It if is not burnt all the way through then there is no need to replace it. It it is burnt to the point of being fragile, then I would replace it. You can get this stuff easily be searching phenolic on Google. Very cheap stuff.