The directory is different in the DM600 than what they say in the instructions, I'm not at home now so I cant check which directory to use. Use a search to find it.
Use the following command in a telnet terminal to find the correct directory.
Code:
find / | grep extepg.cfg
This should find the directory where extepg.cfg file lives, so this is the directory you should be copying to, I suggest you make backups of any files you overwrite.
Other than the above, I think the rest of the instructions provided are good for a DM600.