yea, play it safe and do all 3 files, i tried doing just the custom pack and my phone refused to turn on until i put in the FS and flash as well.... i tried another custom pack with a different region but same code (R8A) and it worked without re-flashing the same flash and FS..
if you do all three, all the rogers branding will be gone... mp3 ringtones will be enabled... as will flash menus... but the shutter tone will stay... not sure why... maybe somebody can help me get rid of that too...
=)