TA at Jubitz in Portland Or. Good or bad?

Took 85 International CO9670 with 580,000 miles on it to Jubitz Ambest in Portland. Had oil leaks & some other minor issues and they tell me all three head gaskets leak. No water in oil, no white smoke, and strong engine. Previous owner did not abuse truck, but did not keep up with preventive maint. as well as he should have.
Gut tells me to replace vlv cover gaskets and oil pan gasket, fix other obvious leaks, and then drive for 100 miles or so and reinspect since engine was steam cleaned and leak locations will be easier to find.
They advise re-sealing entire engine and want several thousand dollars to do it.
Your words of wisdom are greatly appreciated!!!!!!!!!!!!!!!!!

 

original miles. truck used for seasonal co. 4-6 x month 4-5 months/year. guy i'm getting it from is paying to get it into shape before I'm willing to move forward w/it and said he used the shop before, but then he's a bus. owner and not a driver. He only has it to move stage equipment from shop to venue and back. Thank you guys for the advice!!