Amazingly, some of that stuff is DIY (as we well know, having replaced many things in 2 iBooks and 2 Powerbooks that we weren't supposed to touch.... not to mention several hand helds, cell phones, iPods.... Why, yes, we DO have a firewire external hard drive in a LEGO case.... ) But beware - it's not exactly easy and there are no guarantees. If you're not comfortable with replacing, say, the thermostat and water pump on your car, and if you don't have a bench for rebuilding your computer, I'd suggest biting the bullet and taking it to the shop for repair. The part runs around $80 consumer, and labor is going to be about 2 hours. Microdoc says it will be about 120 - 59 for labor and 59 for the part.
http://www.microdocusa.com/ibooks.htmlBut if you're comfortable with DIYing, buy the "Chilton" for your model iBook: here's where we got ours:
http://www.powerbookmedic.com/Take-Apart-Repair-Manuals-p-1-c-258.html Having the take apart manual has been very handy, especially because we've had some issues with case separations in DH's PB.
Which G4 is it, and have you had access to another powercord to make sure that it's the port and not the cord? (Take it to an apple shop or the Genius bar; both can try a second cord if you don't know someone who has another cord.)