replace a 4.7 engine or scrap the truck?
 

My SIL has a 2008 (~100K) with the 4.7 and while her daughter was driving it for the summer it "somehow" stopped running. They have always had it serviced at the dealer so they took it in. NO oil or water. Dealer wants to replace the engine for $7200. Now I am not a mechanic and have never had to replace a motor, but that seems pretty high. Can I get some opinions ???

A dealer will want to replace the engine with a new one, and that price is probably what you would expect to pay for a new engine installed. Since the old engine had about 100k miles on it, you would get yourself back to where you were if you put a used engine in rather than a new one. You could probably save thousands by installing a used or a rebuilt engine, and there are many shops that are capable of doing that.
Keep your options open. There are many possibilities including selling the old car for it's salvage value and replacing it. Dropping a brand new engine into a car with over 100,000 miles on it is probably the option that makes the least financial sense.

BTW, there's something fishy about a story that says the car has always been serviced by the dealership and yet it "somehow" wound up with no oil or water in it. Oil and water don't magically disappear from an engine that has been properly maintained.

I second that

I agree with you on the no warning of this. My niece would only notice an oil or water leak from the car if it got on her shoes.
I am not close to the situation and I am only getting my SIL's side. Her daughter has trashed two vehicles (hers and then Mom's ) in the past month. With a few questions mom tells me the truck did not overheat " in fact it was still on cold after she drove to work"
Any way I think they are leaning towards replacing the vehicle vs repair.
The best quote I got locally was $5700 to rebuild as long as the block was reusable. Thank you for your opinions, I tend to hold onto vehicles too long and dump money when I should just walk away.