Most likely the Freightliner price included replacement of all the fluid in the system as well as flushing not just what was in the tank.
Wolfe10 gives very good advice.
I had hydraulic pump failure and you do not want to take any chances with the hydraulic system as it can cost you upwards of $4000 dollars to fix a single part in the system. There are several, steering box, hydraulic pump, hydraulic fan motor and hydraulic blocks. When you get contamination from a failed part the whole system should be flushed 2 times. This requires much labor to disconnect all the parts and flush the system which includes the hydraulic cooler.
In my case finding a pump was a 30 day nightmare as Spartan had 0 on the shelf. There are others on the net that have had the problem. Search motor home hydraulic pump failure.
Absolute cleanliness when messing with hydraulic systems.
Pogoil.