Identified coolant leak

Hi,

First time poster here.

Have been driving my skoda Superb 2011, 1.4 TSI for 5 years now and barelry had any issues, but looks like small things are coming out. Had just an issue where lost power to drivers door, but after reading forum found that it is common issue and the wire snap after some time, which I was able to solder and put back, so far so good. 

But now noticed white smoke coming from the engine when stopped at traffic light, a bit panic kicked in, but then the sweet smell gave me a hint that it must bee coolant. After few trips, it looks like I have identified the leak.

I have attached pictures, the bolt is nice and tight, looks like the 0 - Rings needs replacing? If so what size I would be looking for? 

It looks like simple job, anything I would need to watch out? 

Thanks