Heres the guide to gain access to the HD: iFixIt HD Guide
If you are not using your optical drive, consider replacing it with the SSD instead. Here's the guide to take the optical drive out: iFixIt Optical drive guide.
In either case you'll need a 3.5 to 2.5 bracket (depending on which way you go you'll need different bracket types) and in the case of the optical drive the addition of a optical to HD enclosure Optical to HD SATA enclosure
I would strongly recommend getting a Firewire (if you can still find one, it's getting hard) or USB HD enclosure to house your old HD as a backup drive and using it to prep your SSD. Or use this kit: Universal Drive Adaptor to prep the SSD before you install it.
And lastly, the SSD you get must be able to run at SATA II specs
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Transform any bare hard drive (SATA or IDE) into an external storage solution. Compatible with all G3 Lombard and Pismo PowerBooks, all G4 PowerBooks, all iBooks, all Mac Minis, all G5 and Intel iMacs, all MacBooks, all MacBook Pros (excluding MacBook Pro — 50+ available at 29.95 each.