Newbie questions about inlet manifold and plenum chamber

I have a 2002 Octavia 2.0l (AZJ) petrol.

Looking at the spark plugs and injectors I see they are covered by the whole inlet manifold and plenum cover.

Is the silver part the plenum chamber? Is this easy to remove to access the parts underneath? What is the best method to access the plugs and injectors?

Would it be advantageous to upgrade the HT cables with ones with rubber boots and a good 8.5-10mm insulation? I had once had Magnecor competition cables on my old alfa and it run great on those. Just curious why they have some metal kind of boots on them.

Also is the picture attached the precat O2 sensor?

I have a lot to learn about this engine.

Many thanks