If you can run the command
rospack find magni_bringup without errors, then you should have what you need on the workstation.
You can run the regular updates, and it is recommended to do so, but DO NOT upgrade Ubuntu versions. The graphical updater makes it pretty clear when asking to move between Ubuntu versions, it is unlikely to happen accidently.
The communication between the robot and the workstation is done through wifi. Both the robot and the workstation need to be on the same wifi network. After this, you can use SSH to log into and run commands on the robot. ROS can also work over this wifi connection, allowing ROS messages to be passed between robot and workstation.