2012 cascadia dd15 blown head gasket

So my stress meter just went up. O/o here truckin fine until this happens. I was losing coolant about 1 gallon a every 3-4 days. had an oil analysis done at speedco and it came back severe high on potassium and sodium which indicates coolant in my oil. Went to a shop to get a pressure test and they said 100% that i have a blown head gasket. It wasnt a commercial truck shop but he has worked on them before and he is 100% its a blown gasket. He quoted me $12,000 to get it all done. Says he'll send it to a machine shop and he does all his work right and good etc.

This is my first experience with a blown head gasket in any vehicle. Does that price sound fair to you guys? Im planning to take it to freightliner to have them diagnose it to be sure. But they are gonna charge 200-400 just to look at it. And im sure they will charge more to take it apart to look at it.

I need to get back on the road and work because i still have a truck payment etc. any advice or experiencr will help. Thanks a lot in advance.

Trucks also giving me an eec 61 spn 4364 code. Could that be related?

 

Ok so 12k is high then?

 

Ok. What would be a fair amount for a blown head gasket? 8k-9k?

 

Parts wise how much was the head and new gaskets?

 

Ok. Thank you for the info. Hopefully there isnt anything else they find. The guy said it takes about 10 days to do. Does that sound right or is he trying to charge a lot for labor?