You're new to Symposium/Call Center Manager, right?
ACD and NACD (Network ACD) calls are calls routed by the switch, not the Call Center Manager. In a perfect world, there should be zero ACD and NACD calls. It means that the script is not controlling the call and the switch has picked it up and "default" routed it.
If you are seeing a lot of ACD calls, then you should double check your system to make sure it is configured properly.
There are no canned reports that break out hold time. However, Nortel is collecting the data, so you can create a custom template report to include it. The Call Center Manager version contains a report writer wizard, or you can use crystal reports or if you are database wizard, you can use other tools to extract the data.
You need to walk before you run, so get comfortable with the Data Dictionary. If you do not normally work with databases, this will take you a while to come up to speed.