I've talked with people who have software for the RF-310M-HH and its not a big deal to program those radios, at least for conventional frequencies. If they are like some others in the series you can keyload the Citadel encryption from the front panel and since they don't have Type 1 crypto, no restricted keyloading device is needed.
Do you know if they purchased the programming software and radio together? Purchased together, from L3HARRIS, the software and the radio would already have the appropriate generated private and public keys, to allow the software and radio to authenticate the mission plan to be loaded. Those keys are not the same as COMSEC keys. They are just for allowing authentication of the mission plan, that's created with the programming software. Without the authentication process the mission plan can not be loaded. The private and public key can be changed, but a new public key can only be loaded into the radio with an AN/CYZ-10 or KIK-20.
When it comes to COMSEC keys and from the documentation I've seen, the RF-310M-HH can be set for VULOS Encryption and P25 Encryption. There are 2 different types of VULOS encryption that can be used with the RF-310M-HH. VULOS TYPE 3 and VULOS TYPE 1. The TYPE 1 and TYPE 3 being described here, are L3HARRIS's terminology for the key types.
VULOS TYPE 3 uses AES and DES Sovereign Keys. Those can be loaded via USB or a Flash drive. VULOS TYPE 1 uses AES (TYPE 1) Keys and those can not be generated by the programming software and can only be loaded with an AN/CYZ-10 or KIK-20.
P25 only uses TYPE 3 Keys and those can only be loaded with a KVL-3000+. I still haven't found any information that indicates the RF-310M-HH supports P25 trunking. I've only seen reference to P25 conventional.