Worked out pretty much as intended.
1) Removed the current cert from the repository which blanked the VPN clients selection. There some warning and push configuration messages.
2) Opened the trusted CA server object and used the Get button on the OPSEC PKI Tab to install and accept the new root cert.
3) Repeated step 2 for the subordinate CA.
4) Used the add button on the IPSEC page to create a new cert. You'll add a nickname and in our case it was important to pick our subordinate CA in the "CA to enroll from". First time we selected the root and we received an error telling us the cert chain was off.
5) Pushed the generate button and added our DN.
6) Another member of our team took the info and processed the cert with DigiCert.
7) Used the returned, signed cert to complete the enrollment.
😎 Switched the VPN clients to authenticate using the new cert.
9) Pushed policy for good measure.