Rocker cover removal

[emy]

Hi,
I noticed some leak around the rocker cover/injector (the last one, on the right side, as i look at the engine). Nobody could trace it, a mechanic replaced the copper seal of the injector, (I do not believe him) but still oil around that area, at the bottom of the injector is dry/clean. I decided to go on my route to find the root cause of it. I covered the injector with a piece of cloth and drove away, after a few days I noticed that the cloth was oily on top of it, not under. Next step, I covered the rocker cover breather seal top area, again after few days of driving I opened the bonnet, removed the engine cover and noticed that the injector was not oily at all, even the area was ok, only under the cloth of the area I covered was oil. I am more than 90% that the leak is coming from the rocker cover little hole from the picture attached.
I have a new rocker cover and want to replace it.
I want to ask if I go ahead to remove all the screws of the cover, which way is the best, with the engine cold or warm? The screws could give trouble in terms of removing them? I am familiar with screws tightening, just asking someone who has already removed/replace it.
Thank you.

[emy]

Tried of removing it, all the screws were easily removed, were not so tight, as per Volvo recommendations, I think around 10Nm.
I could not get it out because of the injector pipes....anyway I have to get a mechanic to do it.
I put it back, I hope is not going to leak around it.

[emy]

Finally I did replace the rocker cover, it was quite easy. The old one was not that bad at all, except the crankcase breather valve oil separator membrane which has a few holes in it, holes through which the oil came out (the bigger one I did it trying to take it out). Now no more oil, let the injector to dry out.
There was no point in changing only the membrane, the lid of it is not easy to remove it, it brakes easily, better off changing the entire cover.
I do not know what have caused the membrane to crack in those places.