Adding a keyless entry to a 1999

We have a 1999 Windstar and we didn't get a keyless entry when we bought the car.

What do we have to do to add one? Are the internals all in the car and do we just have to find a remote, or do we have to get something else?

I'd call a ford dealer & see if they can run the VIN# to see if your van is equiped with keyless entry. If so, pick up a remote on eBay, program it per your manual & you are set.
G/luck
Joel