The manufacturer does NOT have to replace the entire car! Your warranty specifically covers details. If the car was unsafe for some reason and could not be repaired, a replacement would be warranted.
A few years ago a friend bought a loaded V8 Buick, only to have the engine replaced after a few months as it seized up. It did not affect the resale value; these things happen. Many Oldsmobile diesels were replaced with gasoline engines and happily served out their time as taxis. Since the cars had a generally bad reputation it may have affected the resale value.
To save time, accept the dealer’s offer and live happily ever after.