My fiancé has an old moto x, I am looking to upgrade her to the G4 for Christmas. Is it a simple SIM card swap out or is there more to it?
the SIM in the Moto X must stay with that phone (a CDMA phone the SIM is just access to LTE network when phone is registered on the network it does not link the phone to your account or number)
you need to buy a Republic 3.0 SIM
from Amazon Republic-Wireless-Starter-Prepaid-Carrier
then activate as a line replacement Activate My Phone
also note you most likely be moving to the GSM network for the Moto G4 Coverage Check GSM | Republic Wireless
also the Moto G4 needs a 3.0 Plan No Contract Cell Phone Plans without the hidden fees | Republic Wireless