My bike inexplicably fell over (it was leaning on the kickstand and fell over opposite the kickstand. I still don't understand how this happened because I even tried a test tilt from the same position and it would always fall back onto the stand - but I digress.)

The full weight of the bike fell onto a short concrete wall immediately next to it, and the point of impact was the right-side front fork tube. The tube then cracked right where the bike hit the wall.

See this album with pics and video of the crack.

Here are my questions:

• I actually thought the bike was fine after the fall (the total fall distance was only like one foot or less), but I just hadn't noticed the crack initially. I already drove it for about an hour before later visually noticing the damage. Is this still safe to ride? Will driving with a cracked front fork tube risk the safety of riders? Will it risk further damage to the bike?
• I'm not 100% sure what the pipe is made of. I'm actually surprised it cracked so easily. Is the damage repairable? Perhaps with an epoxy? Temporarily repairable? Permanently repairable? Is it aluminum? Plastic? Ceramic?
• If and when I replace the pipe, can I re-use all the other parts of the fork assembly, or must some parts be replaced along with the pipe, or is it necessary to replace the entire assembly? In other words, what parts do I need to order to do this repair (see parts list in album above)? Note that the bike is only two years old and only has about 2,500km on it, so all the parts should be fairly new. I only need to replace parts that are broken or will be damaged in disassembly.

Thanks for your help.