Thanks for everyone's comments. I think I'm ready to pull the switch on this! I will check and see if they have the 240mhz board; but for $20 + ship, the 200 may be the most cost-effective way to go.
I hooked the 3400 to a good H-P monitor with mini-VGA connection and got "no signal" on the monitor. I get a chime and I do hear the hard drive working at startup. I have inspected the built in screen with a LCD flash and I see no active display, IE, it's not just the backlight that's out.
Based on all that, and the fact that the seller said the monitor cable was replaced by a pro repair service about two years ago, I am betting that it is the logic board/VRAM issue and not the display or cable. Holler if anyone thinks that logic is in error.