Holy old thread!
The editor I have is BinHexEdit 98 (v0.5.25) from DemonSoft. I haven't used it in ages (and I can't activate it now 'cause apparently I'm missing a driver), but I recall that it is pretty user-friendly. There's probably an update around (it is a 98 program, after all), but I can't imagine what Demon would've added.
Hey, I still have the setup file! Cool. The readme says this is the first release.
The best way to learn Binhex is to look at some of the stats ingame. That'll give you a good frame of reference. Most fan-made opts come with .shp files that contain the Binhex data, and BHE98 comes with a demo.shp that can be used as a template.
"Party." --High Priest Harrar