2017 Engine Sludge= New Engine?

Weird problem. I just bought a used 2017 QX60 with 30k miles on it from CarMax less than a week ago. It is leaking oil and is still under carmax warranty so I took it in. They first told me it needed a new front valve gasket but when they took it apart they noticed that their was sludge in the engine. They recommend that we returned the car with CarMax's 7 day return policy and found something else. I asked about fixing the issue and they said the only solution was the replace the entire engine which I could have them do since it is still under their warranty. The engine work would be done by the Infiniti dealer on CarMax's dime unless Infiniti decided it was covered by manufacturers warranty. We have no service records on the car.

Soooo the question is do you...
1)Return the car and find another one?
2)Keep the car and get a new free engine?

What do you guys think?