Blown Motor? $6,000 fix? $10,000 fix? $16,000 fix? $6 fix? 5.3 LS Woes in a GMC Yukon!

Everyone loves the LS engine family, and for very good reason. They took much of the loved and long running small block chevy and brought it into the modern world. They are everywhere in all kinds of forms, from 4.8 liter versions in work vans and trucks to 6 liter and larger versions in race cars and big trucks. Great design, great performance, and great availability. Unfortunately they DO have one or two issues as well.
This customer has put tens of thousands of miles on his truck for work and personal use but recently had a sound coming from the engine bay and a loss of power. Giving it to a local dealership near his house to be checked out they quickly came back to him with 2 options, one cost a bit over $6,000, the other a bit over $10,000 if the first option didn't work. That's when he reached out to us, we reached out to our transporter at Next Level Transportation (www.facebook.c...) to get the truck brought us.
So here we go, what will we find? Is it dead in the water? Was the previous shop's diagnostic correct? Is our customer 4 to 5 digits deep in repairing his GMC Yukon?
Oh! And Merch!! LucoreAuto.MyShopify.Com