Freightliner Cascadia Head Gasket Leak “OUTER”.

07/25/2020 @ 2100

Seeking advice...
After chasing an antifreeze leak for over a year; it has come to a “outer” HEAD GASKET LEAK. I had the oil coolant housing “gasket”, changed and upon removal; we noticed the leak from the head gaskets and not the oil coolant housing. We replaced the oil coolant housing gasket and installed a missing bolt that holds the housing. I asked the mechanic if he saw any contamination in the oil when he changed the oil and during the repair; and he said “no”. Nor are there any contaminations in the antifreeze reservoir nor on the oil dip stick. I drive the rig within a 75 mil radius for no more the 300 miles a day, but something 150 miles, and after working the entire week and stoping on Friday evening; I checked for leaks ie. residue around the head gasket or around the oil coolant housing, and oil dip stick and hoses. There was a some residue outside the oil coolant housing but not as much as previously before the gasket was replaced. No contamination on the oil dip stick either, nor any residue around the hoses which were my first tell, tell signs or warnings from the beginning of the chase.
I’m a fairly new owner operator with a 2015 Freightliner Cascadia with a DD13.
I drive to the Ports of Long Beach, and home every night, mechanics abound, I have some money for the repairs, but one mechanic says he can turn it around in four days, but has yet to give me a price, another says $5000 roughly. What am I looking at as far as price? What is reasonable price? Is there level of kits that can be reinstalled What are my options...?

Thanks for your time and expertise...

Alberto Orozco