Looks that way. Better than putting the plugs back in though, or you'd have had redex trying to get past the rings and into the sump :).
IMO it's very difficult to tell. When the engine is cleared out you'll notice a massive difference. A week of me giving my Mum's Polo a good thrashing transformed it from something that pinked like mad to something actually driveable. After she got the tracking sorted it even steered and stopped properly. All she needs now is a new clutch and to learn what gear to drive in :).
Logic dictates that if there's carbon on the end of the spark plug thread there'll be carbon on other bits of the combustion chamber, like the head and piston crowns. My understanding of it is that the carbon gets very hot and this is what causes the pinking - the petrol's set alight by the heat from the carbon instead of the spark plug. There are other causes of pinking like the timing being out, but that can pretty much be ruled out with your engine as it's not got a dizzy.
How old are you? You must be at least 18 as you've said you're at uni. If she's not serviced her car in 2 years and 4000 miles the oil will be a state. I didn't buy my car but I do get to do whatever I want to do with it maintenance wise. Which means the valve clearances actually get checked, the air filter gets change and oil changes are every 5k or so, whereas my Dad subscribes to the "It'll be fine" school of thought. I'm don't want to have a go at your family, but from what you've posted before they've managed to melt metro engines and destroy pistons with pinking, and if I were you I'd ignore what they've got to say regarding the oily bits of a car.
Lucky you :). Looks like my rocker cover is leaking oil again, so I need to check the breather pipes. I ought to rivet the spare wheel hanger back on too :).