Gotta get the handlepost off before you can remove the fork on a Dahon. The procedure is probably not difficult if you know which bolts need to be loosened to remove it. If you don't, and you start loosening every bolt in sight on the handlepost in an effort to remove it to get at the fork, you're creating a headache you don't want, as it might take awhile to get everything back in proper adjustment.
So my advice is, unless you're replacing the fork or rebuilding the headset, don't go messing with fork removal. Perhaps Thor will chime in on degree of difficulty.