The base engine in the Monterey is the
Essex 4.2L V6. In fact, that's the only engine. It's paired with a 4 speed automatic transmission.
The Monterey was originally a replacement for the Mercury Villager minivan, which was nearly a twin with the Nissan Quest. All Montereys were made in Ontario, Canada. That plant has since been retooled for building the Ford Edge and Lincoln MKX crossover.
The Freestar/Monterey line was never very popular with consumers, leading to low sales. For its price, there were much better options from Buick and Chrysler among the domestics, and several others if you include the imports from Toyota and Honda.
The retail price on the Mercury Luxury was $28,5000. They do not retain their value well, which is good news if you plan on buying one used in the near future.
You can find these used in a lot of places, including Ford dealerships. For the lowest prices, look online on places like eBay.