E350 Class C Major Problems

While not helping much I recommend going to a non dealership mechanic. The engine likely only needs a part changed such as a bearing or piston rings. Dealerships love to replace entire items when simply changing part of a item will fix the problem.

In your case why did they say the entire engine needed replacing? Short of severe overheating or catastrophic mechanical failure I can't think of something that would wipe out a engine.