Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
If you get a 2.5" enclosure with the HD then you can use CCC, SuperDuper, SilverKeeper or similar, to make a clone of your internal HD, then you can switch the two HDs (either yourself, if you're up for it, or, maybe better, get an Apple Service Provider to do it for you for a fee) and then you have your old internal HD resurrected as an external HD complete with instant backup.

I did this when I changed HD on my old Pismo and it worked like a charm. (I could even boot from the old internal disk in it's new USB enclosure. Just note that the PowerBook G4s can boot from USB, so you need a Firewire enclosure to do this.)
 
Replacing a HD in a PB isn't that hard. I would go to iFixIt formerly PBFixIt.com for guides and parts (or go else ware), and search these forums for threads like and [URL=https://forums.macrumors.com/threads/179602/[/URL] and [URL=https://forums.macrumors.com/threads/132599/] this one.

Instead of a drive enclosure you can also get a cheap USB to IDE connector for about $20 U.S. I don't trust TigerDriect because the denied a rebate that I know I did correctly. Search for Cables Unlimited USB 2.0 to IDE Cable with Power Adapter. I used one to transfer data from my busted iBook.

Connect the new drive to your enclosure or the USB adaptor and then have at cloning.

Generally I zero out all new drives then partition (set number and size to what ever size you want), rename, etc...

Then I use Carbon Copy Cloner, but others like Super Duper. SilverKeeper is another option. I have used SK, but I don't like it very much. CCC is not free, but it's demo is limitless. It costs 5$ U.S. SK is free. SuperDuper is nearly $30.0 U.s. Always check your clones, and always follow the directions.

Before you clone, I recommend running, some sort of system health utility, or run the standard scripts in terminal.
The utilities I recommend using (use one not all) areONYX or Main Menu. These are good maintenance utilities. MacSweeper is for 10.2 and before. I use Main Menu, but ONYX used to be my favorite. They also allow access to other features of OSX that you might not easily find through the normal GUI if at all. Currently MainMenu is being updated to both work with the latest Tiger update, and massive improvements and additions for sale as a pay app. For now it's free.

Lastly clone the drive. It's easy.Carbon Copy Cloner, but others like Super Duper. SilverKeeper is another option. I have used SK, but I don't like it very much. CCC is not free, but it's demo is limitless- so it is free for those who see no value in it. It costs 5$ U.S. SK is free. SuperDuper is nearly $30.0 U.s. Always check your clones, and always follow the directions.

Check you clones!
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.