yes, install a clean OS first (3.0 hasn't been properly tested but it should work, I think gulliver would be more than interested to hear the result)
extract the lha package to the HDD, move all the contents of the dir, overwrite all the files in sys: with the contents of the directory BetterWB.
then run the BetterWB_Install, after that, you can delete the BetterWB_Install file.
I'm running into "Directory locked" when trying to execute WBStartup+prefs
my WBStartup folder is empty