Hi Jason,
The first step will be getting a copy of all the certificates and keys either by using a backup of the files or by exporting them from IIS
Once you have the files, you will have to manually import them into the ACE following the instructions below:
http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/ace/vA2_3_0/configuration/ssl/guide/certkeys.html#wp1012347
One thing I would like to highlight is that one recent releases, the "crypto import bulk" command was introduced. This command allows you to import several files at once from an external SFTP server. The use of this command is also explained the link I sent.
Please, do not hestitate to contact me again if you need further clarification on any of the steps involved in the process.
Regards
Daniel