Upgrading from 10.3.9 to 10.5 — pitfalls?

I run a single CPU G4 1 Ghz Xserve with 2 gigs of ram. This server only does SMB and AFP file sharing, nothing else. It has one of the hot swap drives used for the system, and one larger hot swap for the files it serves. A third drive holds a copy of the file drive, that I currently manually duplicate, something I hope to automate with this upgrade. (Rsync won't do extended file attributes in the version in 10.3.) Are there any major pitfalls I am going to run into in this upgrade? The clients do authenticate, but the file access is also unrestricted, as I have no need of file protection (although I do plan to do some things different after the upgrade, things that didn't work very smoothly in 10.3, such as OD setup.) Would doing a carbon copy clone to an external firewire drive of the boot drive be a good thing to do before starting this upgrade? The system can boot from an external FW400 drive, can it not...? (in an emergency). Thanks for any tips or pointers. :D :?