The power steering control electronics and electric hydraulic motor are a self contained single module. Its fitted in the front corner of the car under the nearside (passenger) headlight on the outside of the chassis leg. You need to remove the headlight to see the filler cap for the fluid reservoir to check the level and top up but to work on the pump you need to remove the wheel and plastic wheel arch liner. The power steering controller itself is a simple affair and doesn't have a non-volatile memory so it sends it faults for storing to the instruments. I have had that message when clearing my dash instrument errors so I wouldn't worry about that so much.
The power steering module communicates with the dash to get road speed and the engine ECU to get engine speed. The speed information is important as the assistance level is dependent on road speed. High assistance a low speed and parking and load assistance at high speed. As having the correct amount of assistance at the right speed is a safety issue, if the steering module sees an interruption in communication or something that's unexpected, it goes into "emergency mode" with low assistance. The warning symbol you are seeing is shown when the steering is in "emergence mode" and the steering goes heavy. You also get error 00566 stored in the dash for this.
00566 can mean that there is an interruption or issue with the CAN bus communication or it can simply mean that the steering has going into "emergency mode" for another reason. Have you checked the fluid level since you had the leak? Is it correct? If its not correct I would check the connectors on the pump for corrosion and the wiring for damage. The CAN bus wiring from the steering connects to the ABS CAN bus wires in the engine bay before going into the interior of the car to get to the dash so if there was a wiring issue further in then I would expect to see problems with the ABS too.
Regarding the comment about steering angle, early cars have a "G250" steering angle sensor on the steering rack itself for measuring the wheel position. There are separate fault codes for this if G250 it is faulty as this is wired directly to the steering controller. Later cars don't have this sensor and use the measurement from the steering angle ring sensor in the steering column inside the car for this. The steering column angle sensor has built in electronics and other modules such as the ABS and power steering read the angle via the CAN bus from the sensor. A problem with this module could be recorded as a communication error fault code.
If you want to check the CAN bus wiring using a multi meter, I would suggest that all modules on the bus are disconnected first to prevent any damage. That is steering pump, ABS, engine ECU, dash and steering angle. Then check steering 4 pin connector pin 1 to dash green pin 19 and steering pin 2 to dash green pin 18. You can also check the steering angle sensor wiring, pin 5 to dash green 18 and pin 4 to dash green pin 19.
If the fluid level is OK, there isn't corrosion on any of the connectors and the wiring is fine, there could be a problem with the steering angle sensor.
regards
Andrew