2002 Honda Accord Engine Replacement

Olil leaking from under engine took car into Honda Dealer. Paid $2600 because Dealer found oil leaking from cylinder head gasket due to engine over heated due to faulty radiator fan switch. No warning light ever came on when I was driving the car. Dealer installed a special order head gasket and seals, radiator fan switch, retorqued all hardware to factory specs bleed cooling system. Took the car home, twelve days later, I noticed oil leaking again. I took it the dealer, now I am being told the engine is warped and a whole new engine is needed! Is this common? I can believe the Dealer is making me put in a new engine, when they seem to have diagnosed the problem wrong the first time.