Only shipping limitation to USA is for registered and unregistered mails. EMS is working always.
Starting from last December all post offices around world got notified that AirMail packets 500gr or over will be stopped at the borders and they go trough extra security scans etc. That can delay shipments a lot or even worst cases totally destroy.
All assembled kits will be shipped with EMS so no worries about that.
This rule is made by umm "Homeland security office" or similar. And latest knowledge what we have is that this rule ends on 10th of March but well last time they said that it would end on 8th of Feb so who knows...
For basic operation there is no any specialties. How to set up your radio is also depending highly on which software you plan to use. ArduCopterNG, ArduPiratesNG is rather different comparing to our ArduCopterMega software. Ok they all uses first 4 channels as normal flight eg, aileron, elevator, rudder and throttle. Differences are on AUX channels and how those works.
I have not looked latest ArduPiratesNG code but i think they still have GPS hold on one AUX channel and Acro/Stabile on other. ACM then again uses one channel to switch between different flight modes (can have 5 pre-programmed modes), one channel is used for PID tuning/camera offsets and 3rd aux for in-flight level tuning.
KIT has nice "octopussy" cable so users can easily swap their pins to different order if needed. Not all receivers have ail, ele, thr, rud, aux, aux, aux channel order. Tho throttle is usually always on ch3 :)