I hope your session goes well! When you get the gun running, a x39 AR is very, very fun. Both I and my son love them, my son says he really prefers that caliber over .223 to shoot.
Been awhile since I handled an AK, but the AR has nice ergos and handles nicer than the SKS. A bit lighter. The .223 makes noise, but has very minimal felt recoil, almost like a loud .22. I have several full-sized 30 cal rifles both in bolt and semi-auto, those really whack you good. The x39 is in the sweet spot.
The Duramags have been completely reliable, I don't mind the relatively higher cost since the BCA upper is priced so low. 4 reliable mags instead of 10, you will never know the difference functionally.