Melinda;
-> if you use the tools depot option in the unity server you will see an option called dc\gc reconnect tool to check if unity looks at itself as a domain controller; here is a link that will give you more informaiton on this tool; http://www.ciscounitytools.com/Applications/Unity/DCGCReconnect/Help/DCGCConnectionManager.htm
-> Can you clarify if you are asking whether the unity reference account ( unityinstall/unimgstoresvc/unitydirsvc) needs to be domain admin or not ? If you query is related to the above mentioned accounts ; what permissions do they need is documented in the following link;
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/unity/5x/installation/guide/umexfo/5xcuigumefox/5xcuigumefo070.html
-i hope this helps.