Verifying Failed GeForce 8400M GS

I have a Dell Inspiron 1420 that was misbehaving; on start-up, the monitor appeared "dazzled". Disabling the GeForce 8400M GS allows it to start and function with what I assume is the less-capable but at least functional built-in video. I believe that the GeForce chipset has failed and I'm thinking of replacing the motherboard, which I understand is the only way to cope with the failed GeForce video "card".

How can I verify my diagnosis? I ran the Dell diagnostics from their site, but with this device disabled I don't think it gets tested. I'd like to know for sure that this is the only way to proceed before I buy a new mobo.

I ran System Recovery and Start-up Repair multiple times from the hard drive and from the Win 7 DVD. I've installed the newest GeForce drivers and rolled the driver back to a version from September, 2013, with the same result. These steps have persuaded me the problem is in the HW, but I'd appreciate some reassurance. Maybe I'm putting too much into the reports about the GeForce chip problems and lawsuit for 1420 owners (too late for me).

If I do replace the mobo, I'm inclined to buy one that uses the Intel video chipset instead of the GeForce...to preclude the same problem. Or am I just trading a known GeForce problem for Intel problems that may be worse?

Thanks!