Unfortunately no, the value of your car will not appreciate in market value. You might be able to find a buyer that is willing pay more thinking there is added value, but that falls under the "sucker born every minute" adage.
To clarify: if the engine has 42k on it you are buying a used engine that was rebuilt 42,000 miles ago. A reman engine would be one that was rebuilt and had no mileage before it was sold to you. Any warranty would be provided by the installing shop or thier vendor and should have been the first question you asked when a used engine was offered to you as an option.
When we sell used engines to customers our vendor offers 3 different price points depending on the length of the warranty you want. The quality/mileage on the engine plays a factor in this also. Generally the longer warranty - the lower the mileage - the higher the cost.