Crank axle cracked on 1972 Centurion, looking for guidance on how to replace As I said, I have a 1972 Centurion. Today while riding I hit a pothole as I was coming down on my left pedal. I immediately felt like my pedal was moving around in ways it shouldn't. Stopping to look, I'd cracked the actual axle that the crank arms attach to.

I'm looking for information on where I can buy a replacement part for this, how much it will cost, as well as how to carry out the replacement.

Here's the actual crack: 

Here's the pedal looking all bent:
The crack is in the bottom bracket(BB) axle. This will at least need to be replaced. If the crank arm(silver part) is not damaged this can be reused. 

There are many types of bottom bracket standards but it is most likely this frame has a 68mm English thread square taper bottom bracket which are the most common in pre year 2000 bikes.

Something like a Shimano UN26. Any bike shop should be able to supply and fit a new bottom(price in my local area would be $30-50 supply+fit). You do need specific tools to remove and fit bottom brackets so unless you plan on investing in some tools I suggest get a shop to replace it.