For those interested, I've written perl script at
http://linux.voyager.hr/palmos/ac_fix.perl

It allows you to:
- Edit AutoCorrect list
- Edit Alt Key mappings
- Edit Alt Key Help Screen

Tested on Treo680; but I've done some support and checking on Treo600 and Treo650 files.
So it should probably work on other models too. Let me know if it doesn't.