Well, I answered my own question.
Today I got a SIM from Verizon, added it to my existing plan, and plugged it in to my DUDU7 and it worked without issues. The only thing I had to do after installing the SIM was do a software reboot, after which it showed in the status bar and worked immediately. No APN configuration was necessary. We went this route because the head unit is installed in an rv and we wanted it to have connection for monitoring systems when we leave the vehicle. Hope this is useful to anyone considering the same in America. Thanks.