Hi Glen,
I think you could use the below as a useful guide.
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/hw/nexus7000/installation/guide/n7k_hig_book/n7k_replacing.html#pgfId-1410535
You could copy the current configuration of all vdc to a usb drive and later restore them back to new sup.
copy running-config usb1:configuration_file_name vdc-all
and later copy the config file back to running config on new sup. Kindly go through the above link to understand better.
Hope this helps you.
Thanks,
Madhu