If your oil and trans oil are fine and the coolant does not look like milk I would get a kids pool and dump the coolant then flush with water and have the heater on high. Take that to a transfer dump we also have one here, then take it to Cummins and have them do a coolant flush using Restore about a gallon.
When I did my 06 PSD I used 54 gallons distilled water 1/2 gallon Restore flushed then 1/2 gallon Restore+ from Cummins NW then went back with Delo Cat EC-1 coolant at a 50-50 mix with distilled water.
JR