I've looked up this old thread to place a link to a TV programme listed on a Tube that You might know.
This prog is not technical and for some in this forum, basic and frustratingly lacking in detail! BUT the language used to explain is the kind that the non-technical person will readily understand. It shows what happens on a 'D' check for a 747-400. I Think it will be helpful to the concerned passenger to see how rigorous a check this is and to know that every aircraft - of all types - goes through a sequence of A/B/C/D checks in their working life. Obviously, the example here is a BA machine and shows the best of what can be done.
It lasts an hour but I think it will be interesting and there was one fact I learnt that I did not know before! So that means my anorak is in good condition.
If that does not work, go to the Tube of You and search for:
British Airways Boeing 747-400 in D-Check