To offer answers to some of your questions, no need to apologise for asking questions, better to ask than break something.
There's nearly always a black coating inside a cam box, I reckon it's precipitate from used engine oil - combustion by-products.
The cam followers look a bit rubbed but I think they are fine as long as not wearing through the hard surface. However, the tappet adjusters look worn. You could clean them up - there's threads on this forum - or consider replacing. It's not expensive to buy some Allen headed ones, which I did and this makes setting the clearances a bit easier.
There's nearly always a black coating inside a cam box, I reckon it's precipitate from used engine oil - combustion by-products.
The cam followers look a bit rubbed but I think they are fine as long as not wearing through the hard surface. However, the tappet adjusters look worn. You could clean them up - there's threads on this forum - or consider replacing. It's not expensive to buy some Allen headed ones, which I did and this makes setting the clearances a bit easier.