Remote keyless entry swap

Sorry to tell you that isn't something that can be done easily. Keyless entry is part of the body control module and the GEM. Both of those parts are different between the two years and not interchangeable. Probably the easiest way to add remote locking would be to use one of the aftermarket kits out there, just be sure that it is installed properly as a poor install can make things into a headache. The other option would be to find the parts from a 2000 or use a scan tool and dealer access to program those to match your 2000. The reason for that is that Ford changed the electrical systems at the end of the 2000 model year and only specific items will interchange.