problem with the hydraulics on an Exmark riding mower

My Exmark lazer Z has no power making a turn to the right on a hill. Dealer checked it out and said it is a faulty pump but the whole system needs to be replaced, 2 pumps and 2 motors, because there is metal filings in the fluid and that has been distributed throughout the system at a cost of $4200.

I wonder if flushing the system and replacing any damaged parts or the entire pump might work.