Mac osx backup help

I'm looking around for some advice on backing up an older mac powerbook running osx 10.3.9

What I want to do is backup all my important data and wipe it off the disc, I can handle this part. But I want to leave all my applications, plug-ins with authorizations, etc. on there, then make the best possible image or backup of that, wipe it, clean it, and put that backup of apps back on the machine including authorizations, etc.

So essentially I'm wondering if someone out there knows how to do this. I'm trying to keep my important and obscure apps running, with the least amount of downtime. Some of them require special work for authorizing and setup, like hunting down old contacts and asking for assistance. Some of these are essentially apps built from people or companies that no longer exist or never existed in the first place. You can imagine what a headache that is.

Any help or advice is appreciated!

Thanks for reading.

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