Whether you can work with the IP address on the device heavily depends on your surrounding network. For example, if you work at an institution that requires certain static IP addresses to connect devices to the lab network, you need to change the IP address in accordance with this requirement. But you may be able to use the IP address as is just as well and just need to change it in the device_db.py file.
A good first check is to just ´ping´ the IP address of ARTIQ from the PC you want to use to control the system. If you get a response, everything is ok, otherwise there is some other problem.
Changing the IP address works as shown in the manual, yes.