Booting from Ext Firewire drive

I want to upgrade the HD in my G3 Firewire PowerBook, OS 9.2. My thoughts are:
1)Install new 40G HD in PowerBook, replacing the 6G that came with it.
2) Install original 6G HD in an external Firewire case.

I should be able to boot from the ext HD. Once booted, I can the copy all files to my new HD installed in the PowerBook.