yes, just put the patched hex file on the drive and run the iriver firmware updater.
Also unzip the rockbox build onto the drive so that the .rockbox dir and rockbox.iriver file are also in the root
Don't forget to install the fontpack (separate download) and download/read the manual
If something's unclear, come over to the irc channel (rockbox hosts a simple webclient)
Rockbox dualboots so you will still be able to run the original firmware (but who would want that?
)