These PB 17" logic boards run anywhere from $700 - $900 so I'll tell you want I've done in the past. Look on eBay but especially Craigslist for your PB model where just the LCD has gone bad or better yet, where it has been broke or cracked. NOTE: There is always a chance the video issue is logic board related so I prefer broken LCD models as opposed to ones with bad inverter boards or backlights.

I see these on CL periodically for under $400. I saw one for $300 here in the Seattle area about 3 weeks ago. I have too many PB's now otherwise I would've bought it. If you find one in your area, make sure when you boot the machine, you hear the PB's start up chime. If you don't hear a chime, try restarting again but reset the PRAM.

***Press and hold the Command-Option-P-R keys on restart. You must press this key combination before the gray screen appears.
***Hold the keys down until the computer restarts and you hear the startup sound for the second time.
***Release the keys.

If again you don't hear the initial chime, then try once more booting from your original OSX boot CD you just happened to bring along. Just make sure you hear that chime before handing over any cash. Once you find one, there's plenty of info on the web as to doing this repair yourself.

There are "Take Apart" guides on the web and here are a few good places to start.
Useful Websites:
http://www.ifixit.com (I use these people...awesome service and products)
http://www.ifixit.com/Products/Aluminum-17-Inch-1-5-GHz-Logic-Boards/9/42
http://www.powerbookmedic.com/Take-Apart-Repair-Manuals-p-1-c-258.html
Actual PB 17" guides:
http://www.ifixit.com/Guide/Mac/PowerBook-G4-Al-17-Inch/Logic-Board/55/17/
http://www.powerbookmedic.com/Manuals/17-inch-powerbook-manual.pdf

After the fix, you can easily sell the remainder of the unit as individual parts here on Ebay and make more than half of your investment back.