Will the CAN bus shield actually allow the arduino to process live CAN data?

If CAN data is coming in at the common speed of 500k, does an arduino with the CAN bus shield actually have time to parse and process live data, or is the CAN bus shield only designed to log data to an SD card? If so, where are examples of this? I've looked for about two weeks now and haven't been able to find anything...

Yes, that is the usual purpose of the shield. Have a look at OBD2 loggers - they use the CAN shield.

The 500K speed relates to the bit rate of the individual messages. There are always gaps between messages so you won't get continuous 500kbps data. (It's not an MP3 file.)