The backup is easy if you have the keys and certificates in a file.
Just keep the file somewhere safe.
In case you need to reconfigure the SSLM, you can simply import those files.
If you generated the keys and certificates on a server instead of the SSLM, it is even easier to do as you should already have those files.
If you generated the key on the SSLm, you need to export it.
I would recommend the use of CVDM [cisco view device manager].
It's a free utility that will let you configure the Cat6k and the SSLM from a web browser.
There is a key management section that will help you import/export keys.
http://www.cisco.com/en/US/products/sw/cscowork/ps4565/products_user_guide_chapter09186a0080418c2c.html#wp1178684
Regards,
Gilles.