it IS possible. Unfortunately there doesn't seem to be a repair guide for that specific problem, but you can follow the guide for the 15" Powerbook. It won't be exactly the same, but it should be pretty darned close. Check out this link:
http://www.ifixit.com/Guide/Repair/PowerBook-G4-Aluminum-15-Inch-1-1-5-GHz-Inverter-Antenna-Cables/1023/1#top
This is for the inverter, but the hinges are right there once you get to the inverter. I'm not saying that it will be easy.... in fact getting it back together can be pretty tricky, but it is doable. I've actually done it myself on a 15" powerbook.