2008 Mac Pro Power Supply Issue

Hello fellow travelers.

I woke up this morning (as many a great blues song begins) and my faithful 2008 Mac Pro had crashed (powered itself down).

It won't restart. Nothing. No lights, no chimes, no fan, not a sound, not a murmur. Just me groaning.

I have tried a different cable/cord. Plugged in to a different surge protector. Unplugged - replugged. Danced with the devil.

I have held the power up button down for 10 seconds and released, 20 seconds and released. And so on in vain.

I have made a Genius Bar appointment but this being the July 4 weekend it's not for a couple of days.

I am assuming, in the meantime, that it's the power supply that has croaked.

I don't want to pull it apart yet till the Genius Bar folk have confirmed this (and charged me for the diagnostic pleasure) but does anyone know the model or part type of the Power Supply I would need for a 2008 Mac Pro (Quad Core)?

Also, is installing it something I could do myself? I'm reasonably adept with a Philips screwdriver.

Lastly, is eBay my best resource for finding one or is there a reputable dealer of refurbished or new Mac parts for older Macs that someone can recommend?

Many thanks for any advice even if ts just sympathy.

Cheers.

Adrian S