The EGR does not operate all the time. The ECU takes various signals from things like temperature, throttle position and acceleration and decides how far to open the EGR valve. It's not just a case of it being on or off. Rest assured that the module doesn't do anything dangerous such as messing with fuel injection or timing. The way it works is very simple and because it sends it's signal directly to the ECU it's impossible for it to cause any damage. Even if the module failed for some reason or stopped working correctly the only thing that would happen is an orange warning light on the dash. If this comes up just remove the module and disconnect the battery for 30 mins. The ECU will then revert back to original operation.
The module will only close the EGR valve. It will not have any effect on fuelling, timing or any other aspect of the way the engine works. There is another sensor after the intake that deals with this. It is this sensor (IAT) that people add cheap eBay chips to in order to 'increase performance'. This can be dangerous and the sensor should be left well alone.
As for fitting these it literally takes 10 seconds. I'll post a video up shortly but if you can unplug a connector then you'll be able to fit this! I've spent years looking for the right parts to make this as simple to fit as possible. I know there are people out there who aren't mechanically minded and feel that they shouldn't miss out on the benefits of this module.