I haven't used my Mac Mini in ages and now it wont work. 
When I turn it on, it chimes but the graphics on the screen are all garbled. I've swapped monitors and the vga adapter but still the same problem. I'm guessing the graphics on the mobo have gone.
How easy and cost effective would it be to swap the mobo for another (if indeed, that is where the problem lies)
Is it possible to boot off a live-cd and diagnose the problem via the network port.

When I turn it on, it chimes but the graphics on the screen are all garbled. I've swapped monitors and the vga adapter but still the same problem. I'm guessing the graphics on the mobo have gone.
How easy and cost effective would it be to swap the mobo for another (if indeed, that is where the problem lies)
Is it possible to boot off a live-cd and diagnose the problem via the network port.