Well, the fans and lights on the GC do come on. I am curious if the PS might have a problem though. We'll see. I'm gonna start looking for parts tonight.
The odds are slightly in favor of it being a motherboard issue, but when you replace the motherboard, it is always a good idea to replace the power supply, because they do eventually wear out.
And since you are doing all of that work to replace the board, if funds are available, a little upgrading can be a good thing in the long run.
And when power supplies go, you have to do damned near as much work to replace a power supply, as you do for the motherboard.
Not to mention the fact that you won't be 100% positive that it was a bad power supply when the system goes down again.
Keep the old power supply on hand, just in case, if you test it in a pizza box with the new board and it tests out good.
Eat pizza: An important first step.
Place new board with CPU, graphics and memory installed into opened pizza box.
Plug in old power supply.
Plug in monitor.
Jumper the connections on the board to start the PC.
If it fires up with the old power supply, save it for use as a backup, or test unit.
If it does not fire up, plug in the new power supply and test to make sure the other new hardware is all good.
If it fires up, you are good to go, but testing the old board with the new power supply might be a good idea, if it failed to post with the old power supply.
You might find yourself with the makings of a second work PC, or at least some tested known to be good parts for future use.
