I must respecfully disagree. Again, I'm no ESN expert, but the few links I followed on the subject indicated several people have successfully changed their ESNs.
The first link I posted from ehow may not work on Palm devices. You may also take a look here:
http://forum.ppcgeeks.com/showthread.php?t=20090
I would also suggest posting in the forum specific to your device and checking at XDA-developers as well.
Good luck.